In this article, we assume that you are using the device-dependent caller ID (CLIP no screening) in the customer portal, and that your PBX / device transmits the information to be signaled for your call.

You can also customise the number displayed using the custom caller ID feature in the customer portal or the Cloud PBX, although the range of functions is limited.

Which phone numbers can be displayed?

As a general rule, you may only display telephone numbers that have been allocated to you or for which you are the subscriber. These may, for example, originate from another line registered in your name.

Which phone numbers are not permitted?

Phone numbers that are prohibited by the regulatory authorities are not permitted on our network.

These include, for example, foreign telephone numbers, premium-rate numbers, value-added services and emergency numbers. Below is a list of the most common number ranges, along with information on whether they are permitted or blocked.

Number ranges in Germany

Mehr zu den geltenden Regelungen in Deutschland finden Sie im Telekommunikationsnetz (TKG) § 66k (1) und (2).
Number range Type of service Allowed
0800 Free service numbers yes
0700 Personal numbers, regardless of the location of the connection. Callers always pay the same fee, additional costs for forwarding are paid by the line owner yes
  Numbers of emergency services, public authorities and similar institutions. no
0900 Value-added service with up to €3 per minute or €30 per call. no
0137(1-9) Value-added services where the call attempt is already subject to a charge. no
0180(1-7) Value-added services where the connection costs are shared, which are increasingly attracting attention in connection with dubious call services. no

legal basis

For Germany: Telecommunications law (TKG) ab § 66k (1) and (2).

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Created on: 18. June 2026