No data exists for caller with tel. no. &1

What causes this issue?

You have tried to transfer the data for a caller into the front office.
However,the system cannot determine the caller from the number given.

System Response

No caller data can be transferred.

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.