Current Service Provider

NANP · also called serving carrier, current carrier

The carrier that actually serves a telephone number today — which, after porting, may differ from the original assignee.

The current service provider is the carrier that presently provides service for a given telephone number. Determining it reliably requires a real-time lookup against portability data (the Number Portability Administration Center, NPAC) — it cannot be read off public assignment records.

This is the counterpart to the original assignee: assignment records tell you who a prefix was first given to; the current service provider tells you who serves the number now. The two diverge whenever a number has been ported.

Carrier names are illustrative. The lesson is real: the assignment record (who a prefix was handed to) is not the current carrier (who serves a number now). After a port they differ — which is why an area code, or an old assignment table, cannot tell you who a number belongs to today.

Common misconception.

You cannot determine the current service provider from public NANPA/CNAC assignment files. Those name the original assignee only. Claiming otherwise is a common and consequential error.