To set up call forwarding on a mobile phone, dial a short code and press call: **21*number# forwards every call, **61*number# forwards calls you don't answer, **67*number# forwards calls that arrive while you're on the phone, and **62*number# forwards calls when your phone is off or out of coverage. These codes come from the GSM standard 3GPP TS 22.030, and carriers such as Deutsche Telekom, Vodafone and T-Mobile US publish them on their help pages. On an iPhone, the Settings app forwards all calls; for the conditional types you use the codes. In the US, Verizon uses its own codes (*72, *71, *73), and Verizon, T-Mobile and AT&T all state that calls can't be forwarded to an international number. Loomira is an AI phone assistant for small and mid-sized businesses that answers forwarded calls, turns each one into a structured summary and hosts calls, transcripts and customer data in the EU. This guide covers the codes, the phone settings, the carrier rules and the limits to check before you rely on forwarding.

What types of call forwarding are there?

Call forwarding is a network feature that sends incoming calls for your number to another number, either every call (unconditional forwarding) or only under a condition: when you're busy, when you don't answer, or when your phone can't be reached.

The specification behind it, 3GPP TS 22.082, defines four services:

  • Unconditional: calls are forwarded "no matter what the condition of the termination". Your phone doesn't ring.
  • Busy: calls are forwarded only when you're already on a call.
  • No reply: your phone rings first; calls not answered within a set time are forwarded.
  • Not reachable: calls are forwarded when your phone is off or has no coverage.

"Conditional call forwarding" is the collective term for the last three. In the UK, carriers usually call the feature a "call divert". On many networks, voicemail is itself a conditional forward. Vodafone Germany, for example, presets no answer, unreachable and busy to its mailbox, and Vodafone UK's standard voicemail picks up "if you're busy, unreachable or don't answer in 15 seconds". Setting your own conditional forward replaces voicemail for that condition.

Which call forwarding codes work on most mobile networks?

The codes are defined in 3GPP TS 22.030, Annex B. Type them into the phone's dialer and press call:

Forward all calls:        **21*number#
Forward if no answer:     **61*number#
Forward if unreachable:   **62*number#
Forward if busy:          **67*number#
All three conditional:    **004*number#

Each type uses the same service code with different prefixes (TS 22.030, clause 6.5.2). Shown here for unconditional forwarding:

Set number and turn on:   **21*number#
Turn on again:            *21#
Turn off, keep number:    #21#
Erase:                    ##21#
Check status:             *#21#

Replace 21 with 61, 62, 67 or 004 for the other types. The difference between turning off and erasing matters: after a deactivation, "the registered information shall not be erased" (TS 22.082, clause 1.3.6), so *21# switches the same forward back on. Erasing removes the number.

Enter the destination in international format. Vodafone UK tells customers to "replace the first 0 with +44", and T-Mobile US puts a 1 in front of the 10-digit number. Carriers don't all document every code. Google's own Voice help warns that conditional forwarding commands "may vary by carrier", T-Mobile US lists ##004# but no activation code for 004, and Verizon doesn't use these codes at all.

How do you set the ring time before a call forwards?

Add the number of seconds after two stars: **61*number**20# forwards unanswered calls after 20 seconds. According to TS 22.082, clause 3.3.3, "the value is in between 5 and 30 seconds, in steps of 5 seconds". If you never set it, "a default value set by the service provider applies".

Carrier examples follow the same pattern. T-Mobile US gives **61*18056377243**10# as "a 10-second delay" on its short-code page. Vodafone UK writes the code as **61*number*10*seconds#; the 10 is the standard's code for "all teleservices", so the seconds still land in the timer field.

Be careful with a variant that some carrier pages print, **61*number*20# with a single star before the seconds. By the structure of the standard, a value after one star fills the basic-service field, not the timer, and code 20 there stands for "all bearer services". Use the two-star form and check the result with *#61#.

How do you forward calls on an iPhone?

Apple's iPhone User Guide gives this path:

  1. Open the Settings app, tap Apps, then tap Phone.
  2. Tap Call Forwarding and turn on Call Forwarding.
  3. Tap Forward To, enter the number, then tap Back.

On models with Dual SIM, choose a line below SIMs first. A Call Forwarding icon appears in the status bar while forwarding is on. Apple notes that this works on GSM networks, that CDMA customers should contact their carrier, and that "you must be in range of the cellular network when you set iPhone to forward calls, or calls won't be forwarded."

The Settings screen has a single Forward To field. For busy or not-in-service forwarding, Apple says: "If your carrier supports conditional call forwarding when the line is busy or not in service, contact them for setup information." In practice that means the codes above, if your carrier supports them. Apple also warns that iPhone blocks links asking you to turn on call forwarding, because scammers use them. Set it up manually.

How do you forward calls on Android and Samsung phones?

On Samsung Galaxy phones, Samsung US describes this path: open the Phone app, tap More options (three dots), tap Settings, then Supplementary services, then Call forwarding. Choose Always forward, Forward when busy, Forward when unanswered or Forward when unreachable, enter the number and tap Enable. On dual-SIM models, Samsung's Hong Kong support page adds a SIM choice and a "Voice calls" step. Samsung notes that "availability may vary by carrier and phone model."

For Google Pixel phones, Google has not published a help article on the Phone app's forwarding menu. AT&T's Pixel 9 Pro tutorial shows: Phone app → Sidebar icon → Settings → Calling accounts → select a SIM → Call forwarding → Always forward, When busy, When unanswered or When unreachable → enter a number → Turn on. Older versions of the Phone app show a menu icon instead of the sidebar, as in EE's device guides, so labels vary. If you can't find the menu, the GSM codes are an alternative on networks that support them.

Do US carriers use different codes?

Yes, at least partly:

  • Verizon uses its own codes, per its Call Forwarding FAQs: *72 plus the 10-digit number forwards all calls, *71 plus the number forwards only the calls you don't answer, and *73 turns forwarding off. The confirmation "may sound like a busy signal". The destination must be an active voice line in the US with 10 digits.
  • T-Mobile US uses the GSM codes with a 1 before the number, for example **21*1 followed by the 10-digit number and #, according to its calling-services page. ##21# turns unconditional forwarding off, and ##004# "resets call forwarding to default". You can only forward to 10- or 11-digit numbers.
  • AT&T documents *21* plus the 10-digit number and # to turn forwarding on and #21# to turn it off, on its call forwarding page; wait "at least three seconds" for the confirmation tone. AT&T's own pages don't list conditional codes. Google Voice help gives *61*, *62* and *67* as examples for AT&T Wireless. On its wireless support page, AT&T also states that "call forwarding overrides your wireless voicemail" and that you "can't manage call forwarding online".

Can you forward calls to a number in another country?

Often not, and this matters if your answering service uses a number in another country.

  • United States: all three national carriers rule it out. Verizon: "Calls can't be forwarded to an international number." T-Mobile: "You can't forward calls to international numbers." AT&T: "You can't forward calls to an international number."
  • United Kingdom: EE describes diverts "to another number in the UK", and Vodafone UK to "another UK phone number – a landline or mobile". Neither says that international destinations work, so ask your carrier before you rely on one. On Vodafone UK Pay as you go, "you can only divert incoming calls to voicemail".
  • Germany: 1&1 states for its mobile network that forwarding to a foreign number is not possible ("Eine Umleitung auf eine ausländische Rufnummer ist nicht möglich", 1&1 help center). Other German carriers bill foreign destinations according to their price lists.

Roaming is a separate question. Verizon says forwarding set up before you start roaming "should continue to work while you're traveling", and T-Mobile says forwarding while roaming "depends on the host country's network capabilities".

What does call forwarding cost?

The forwarded leg is usually billed to you, not the caller. The standard puts it this way: "The forwarding subscriber may be charged for the forwarded part of the call" (TS 22.082, clause 1.3.12). Carrier wording:

  • Verizon: "If you don't have unlimited minutes, you'll be billed for all forwarded calls according to your plan." There's "no monthly fee for Call Forwarding on most plans".
  • AT&T: "Forwarded calls are billed for the length of the call", and long-distance charges apply when you forward outside your home calling area.
  • EE: a divert to another UK number "is charged at the call rate for the price plan you're on".
  • T-Mobile US: no official statement found on its support pages; check with T-Mobile.

Don't assume an unlimited or flat-rate plan covers forwarded calls. In Germany, O2's price list excludes forwarded calls from its flat rates, while the 1&1 All-Net-Flat explicitly includes forwarding to German numbers.

How do you check or turn off call forwarding?

On networks that use the GSM codes:

Check status:              *#21#  *#61#  *#62#  *#67#
Erase one type:            ##21#  ##61#  ##62#  ##67#
Erase all conditional:     ##004#
Erase all forwarding:      ##002#

Use ##002# with care: it also removes voicemail forwarding. Vodafone Germany warns that callers are then no longer sent to the mailbox at all. Vodafone UK documents ##002# "to cancel all active call diverts" and 1211 to return to standard voicemail. On an iPhone, turn off Call Forwarding in Settings. On Verizon, dial *73.

Two details. AT&T turns forwarding off with #21#, which the standard treats as a deactivation that keeps the number stored; AT&T doesn't say how its network handles it. And the US carriers don't document the status codes, so check by calling your number from another phone.

How do you forward business calls to an AI phone assistant?

The setup is the same as any other forward: you need a destination number. With Loomira, you order a German (+49) or Austrian (+43) number in the portal, assign it to an assistant and forward your business number to it, as described in the phone numbers documentation. Your existing business number stays the same.

Be clear about who this works for. Because Loomira numbers are German or Austrian, the destination is international for any line outside those countries:

  • US mobile lines can't be carrier-forwarded to a Loomira number, because Verizon, T-Mobile and AT&T block international forwarding.
  • UK lines: EE and Vodafone UK describe only UK destinations, so confirm with your carrier first.
  • German lines: use a +49 number. 1&1 mobile can't forward abroad at all.
  • Your own phone system: the documentation also describes connecting a PBX through a SIP trunk, secured with credentials or an IP allow-list. Whether your provider can route calls that way is worth confirming with them before you rely on it.

A few practical points. On a mobile line, **004*number# hands busy, unanswered and unreachable calls to the assistant instead of voicemail, and **61*number**20# then sets the ring time. Set forwarding up in the network rather than in your router: AVM, the maker of the FRITZ!Box, documents that when the router forwards a call itself, it sends your line's number instead of the caller's. Carriers don't document which number arrives with a network-side forward, so make a test call and check what the assistant sees. Finally, avoid loops: if the assistant forwards urgent calls to a number, that number must not forward back to the assistant. What happens to the calls once they arrive is described on the AI answering machine page.