(Number Portability) The capability of keeping the same telephone number when switching carriers or services. It all started with 800 numbers, which led to local number portability (LNP) and later to wireless number portability (WLNP). November 24, 2003 was known as "Cellphone Independence" day because it was the first time in the U.S. that customers in the top 100 metropolitan service areas (MSAs) could move their telephone numbers to a different carrier. In most cases, landline numbers can also be moved to a cellular carrier.