FRITZ!Box 7272 Service - Knowledge Base
Transmitting a different outgoing caller ID when making calls
Depending on how a call is established, either your Internet telephony provider or your landline telephony provider is responsible for transmitting your caller ID. This means that you cannot configure the FRITZ!Box to transmit an outgoing caller ID that differs from the actual number used to make the call. This is why you cannot transmit a landline number instead of your Internet number or vice versa, for example.
Note:It may be possible to have your Internet telephony provider define which number is displayed when making Internet calls. Your Internet telephony provider can provide you with further information.