1&1 and Congstar are two of Germany’s most popular mobile providers without their own networks. 1&1 runs on the O2/Telefonica network, while Congstar uses the Telekom (D1) network. Despite the different host networks, both carriers support the same standard GSM codes for call forwarding.
Which Network Are You On?
This matters for coverage and troubleshooting, not for the forwarding codes themselves:
- 1&1: O2/Telefonica network. 1&1 also has access to the Vodafone network on some newer plans, but GSM code behavior follows the primary network assignment.
- Congstar: Telekom (D1) network. Congstar customers benefit from Telekom’s extensive coverage, including 5G on compatible plans.
GSM Forwarding Codes (Both Carriers)
Both 1&1 and Congstar use standard GSM codes. Open your phone’s dialer, enter the code, and press call. Replace [number] with the full destination number including country code.
| Forwarding Type | Activate | Deactivate | Check |
|---|---|---|---|
| All calls | **21*[number]# | ##21# | *#21# |
| No answer | **61*[number]**[seconds]# | ##61# | *#61# |
| Busy | **67*[number]# | ##67# | *#67# |
| Unreachable | **62*[number]# | ##62# | *#62# |
| Cancel all | ##002# |
Replace [seconds] with the ring time: 5, 10, 15, 20, 25, or 30 seconds.
Example: Forward unanswered calls after 20 seconds:
**61*+491701234567**20#Generate your specific code with our interactive forwarding tool.
1&1 App and Portal Setup
1&1 offers its own management tools, separate from O2’s infrastructure.
1&1 Control Center App
- Open the 1&1 Control Center app (iOS and Android)
- Log in with your 1&1 customer number and password
- Select your mobile contract
- Look for Call settings or Rufumleitung
- Configure your forwarding rules and save
1&1 Online Control Center
- Log in at control-center.1und1.de
- Navigate to your mobile contract
- Find the call forwarding options
- Set your rules and save
1&1 Customer Service
Dial 0721 96 00 from any phone. 1&1 support can help activate or troubleshoot forwarding.
Congstar App and Portal Setup
Congstar has its own customer portal and app, separate from Telekom’s MeinMagenta.
Congstar App
- Open the Congstar app (iOS and Android)
- Log in with your Congstar credentials
- Navigate to your tariff or SIM settings
- Find the call forwarding section
- Set your destination number and forwarding type
Congstar Customer Area
- Log in at congstar.de and go to Meins (My area)
- Select your mobile plan
- Find call settings or forwarding options
- Configure and save
Congstar Customer Service
Dial 0221 79 700 700 from any phone. Congstar support can help with forwarding activation.
Things to Watch Out For
- 1&1 prepaid vs. contract: 1&1’s mobile products are mostly contract-based. If you have a prepaid or flexible plan, forwarding still works via GSM codes, but check your tariff for per-minute costs on forwarded calls.
- Congstar prepaid: Congstar’s prepaid (Wie ich will) plans support forwarding via GSM codes. Forwarded calls are billed at your per-minute rate.
- Forwarding costs: On both carriers, forwarded calls typically use your included minutes. If you exceed your allowance, standard rates apply.
- No access to host network apps: 1&1 customers cannot manage forwarding through the Mein O2 app, and Congstar customers cannot use MeinMagenta. You need to use the carrier’s own app or portal.
- Roaming: Both carriers follow their host network’s roaming rules. 1&1 follows O2 roaming policies, and Congstar follows Telekom. EU roaming is generally included, but forwarding outside the EU may be restricted or expensive.
Frequently Asked Questions
Do GSM codes work the same way on 1&1 and Congstar?
Yes. Both carriers use standard GSM codes, and the activation, deactivation, and status check codes are identical. The only difference is the underlying network (O2 for 1&1, Telekom for Congstar), which doesn’t affect code behavior.
Can I manage forwarding through O2 or Telekom portals?
No. Even though 1&1 uses the O2 network and Congstar uses Telekom, you need to use each carrier’s own portal and app. The host network portals don’t recognize MVNO customers.
What happens if I switch from 1&1 to Congstar (or vice versa)?
You’ll need to reconfigure your forwarding. When you port your number to a new carrier, all previous forwarding rules are cleared. Set them up again using GSM codes or the new carrier’s app.
Can I forward calls to Safina on 1&1 or Congstar?
Yes. Safina works with both carriers. Set up conditional forwarding with your Safina number using the GSM codes above. Your phone rings first, and Safina picks up if you don’t answer. Learn more about Safina.