Wireless Number Portability (WNP)

WNP is primarily provided by wireless mobile service providers to give their users flexibility in porting their mobile numbers. In GSM-based cellular networks, which use SIM cards, WNP works when the current mobile/cellular/wireless service provider gives a user a porting authorization code (PAC). The PAC and the unique SIM card serial number are used by the new wireless service provider to track and provide wireless service on the same SIM card with the existing number.

Some service providers might also require electronic serial numbers (ESN) and mobile equipment identifiers (MEI). In most cases, the user/subscriber can also keep an existing wireless number and the mobile network code when subscribing with the new provider.