How is the caller ID phone number determined?
The phone number displayed by caller ID is determined by the calling party. For a landline, the displayed number corresponds to the phone number that's registered to the line. For a PRI or SIP connection, the phone system can actually control what number gets displayed on a case-by-case basis.
How is the caller ID name determined?
The caller ID name is determined by the receiving carrier. The receiving carrier queries a CNAM database to determine the name registered to the provided phone number.
It is also important to point out that there is no "standard".
However, unlike Local Number Portability (LNP), caller ID is not regulated by a governing body such as the Federal Communications Commission (FCC). Rather, the service is essentially a patched together network of decentralized and databases that frequently operate with outdated information.
So in some cases, the way we send the Number to a carrier may get dropped along the way if it goes through a carrier that isn't configured correctly or to use the same process we are using.
For further information , please see: So How Does Caller ID Work Anyway?