UK mobile network Checked September 2026
Gamma Mobile call divert codes
To divert calls you don't answer on Gamma Mobile, dial **004*, the number, then #. That one code also covers calls when you're busy or out of reach, and #004# switches it off.
- One code for busy, unanswered and out of reach
- All calls: **21*
- Runs on the Three network
**004*07700900123#Dial it from the phone you want to forward, then wait for the confirmation.
- Turn off
All Gamma Mobile call divert codes
Replace NUMBER with the number you want calls to go to.
| Divert calls | Turn on | Turn off |
|---|---|---|
| No answer | **004*NUMBER#
Off: #004# | #004# |
| All calls | **21*NUMBER#
Off: #21# | #21# |
- The **004* code diverts calls when you are busy, do not answer or are out of reach, all together. Gamma does not publish separate codes for each.
How to divert calls on Gamma Mobile
- 1
Check when calls will divert
This code sends calls you do not answer to the destination number.
- 2
Dial the code
From your Gamma Mobile mobile, dial **004*NUMBER#, replacing NUMBER with the number calls should go to.
- 3
Check the result
Follow any prompts on your phone. If the request is rejected, check the instructions for your service before trying again.
- 4
Test it
Ring your number from another phone without answering it. Check that the destination receives the call. To turn it off later, dial #004#.
How to turn off call divert on Gamma Mobile
Dial the code that matches the divert you set up. Calls go back to ringing your phone as normal.
- All calls
-
#21# - Busy, no-answer and out-of-reach diverts
-
#004#
What to know about call divert on Gamma Mobile
One code for three situations
Gamma's conditional divert, **004*, sends calls on when you're busy, when you don't answer and when your phone is off or out of signal. Those are the same three cases that go to voicemail as standard, so setting it swaps voicemail for your number in all three at once. Gamma doesn't publish a ring time setting.
Switching a divert back on
After switching a divert off, you can turn it back on to the same number without typing it again: dial *004# for the conditional divert or *21# for all calls.
Moving an existing phone to Gamma
Gamma asks you to delete old voicemail numbers and diverts from the phone when you move it to Gamma Mobile, so they do not clash with its voicemail. Gamma voicemail is on 121, or 07782 333123.
Divert calls from your phone's settings
Your phone may also offer call forwarding in its settings, depending on your device and plan. The iPhone Call Forwarding switch sends every call on. Use a supported no-answer option if you want your phone to ring first.
iPhone
- Open Settings, then Apps, then Phone (on older iOS, Settings then Phone).
- Tap Call Forwarding and switch it on. If you use two SIMs, choose your business line first.
- Tap Forward To and enter the number calls should go to.
- Go back. A forwarding icon shows in the status bar while it is on.
Android
- Open the Phone app, tap the three-dot menu, then Settings.
- Tap Calls (or Supplementary services, depending on the phone), then Call forwarding.
- Choose When unanswered so your phone rings first and only missed calls move on.
- Enter the number, tap Turn on, and pick the right SIM if asked.
If the code doesn't work
"Connection problem or invalid MMI code"
The network did not accept the request. Check you have signal, turn off Wi-Fi calling and aeroplane mode, then dial the code again exactly as shown.
"Setting activation failed" or "unsuccessful"
The network refused the divert. Some plans block diverts to other numbers, and some networks want the number in international form. Check the notes on this page, or set it up in your phone settings instead.
Calls still go to voicemail
Voicemail is itself a divert, and only one can be active for each condition. Setting a new divert replaces the voicemail one. If calls still reach voicemail, cancel all diverts and set yours again.
Gamma Mobile call divert questions
How do I divert calls on Gamma Mobile?
Dial **004*, the number, then # to divert calls when you are busy, do not answer or are out of reach. To send every call straight to another number, dial **21*, the number, then #.
How do I turn off call divert on Gamma Mobile?
Dial #004# to switch off the busy, no-answer and out-of-reach divert, or #21# to switch off the all-calls divert.
Can I set up call forwarding on Gamma Mobile without a code?
Yes. Gamma says call forwarding can be added from your phone's settings menu as well as with the shortcodes.
What network does Gamma Mobile use?
Gamma Mobile uses the Three network. It is a business-only service, sold to companies rather than consumers.
What is the Gamma Mobile voicemail number?
Dial 121 from your Gamma Mobile phone, or 07782 333123. Calls you miss go to voicemail as standard until you set a divert.
Sources
Checked in September 2026 against the official pages below. Networks change codes and prices, so if something here stops working, their page is the final word.
