FRITZ!Box 7430 Service - Knowledge Base
Two telephone numbers are displayed for one call call in the call list
The caller signals both telephone numbers as his own number. In addition to the number actually assigned by the provider (Network Provided Number), the caller also transmits a telephone number he chose for himself (User Provided Number). The FRITZ!Box displays both numbers in the call list; the first number is the user provided number, followed by the network provided number in parentheses. If the FRITZ!Box should not accept these calls, set up a call block for the user provided number.
Companies with large PBXs may use a user provided number to direct calls to a certain number (for example to the reception desk or the switchboard). Call centers also like to use user provided numbers (for example toll-free telephone numbers) that are completely independent of the number assigned by the provider.
Often you can call both numbers back. The network provided number is the telephone number that the provider assigned to the telephone line. This means that it is the "real" telephone number and can always be called back. However, the unlike the "real" telephone number, the user provider number could have been manipulated by the caller since the telephony provider does not check whether the number is correct ("no screening").