"Number Portability (NP) allows subscribers to retain their Directory Number (DN) when they change their service provider (service provider portability)@ location (location portability)@ or service (service portability). The focus of this specification is to allow PCS1900 systems to support ""service provider portability."" Location and service portability are outside the scope of this document. This specification addresses a basic voice call. The impact of number portability on Short Message Service@ Intelligent-Network-based services@ data services and other supplementary services is outside the scope of this document."