ANI (Automatic Number Identification)
is a service that provides the receiver of a telephone call with the number of the calling phone. The method of providing this information is determined by the service provider (such as AT&T, MCI, Sprint, and so forth).
ANI / Caller ID Problem
When you get Anonymous on the caller id, It is not the problem of the DID but the problem in the carrier which is sending the call to in general.
To confirm if there is a problem, have some one locally in that area code call that DID number and check then the caller id in the DIDX logs.
If the problem is still there, Please contact DIDX then.
When u call from Singapore to a Australia Number, the carrier may not send the caller id sometimes, and when this happens, you get Anonymous on the caller id.