(FORTUNE Magazine) – Aggravated cellphone users can breathe a sigh of relief. Come Nov. 24, customers can switch carriers and hang on to their numbers. According to a May study by the Management Network Group, about 8.8 million of the 146 million U.S. users say they'd switch the day after local number portability (LNP) goes into effect. We checked in with wireless analysts to see who'll get the call. --Muoi Tran

Company Why Gains/Loses Customers

AT&T Wireless [Gain] 21.5 million A strong brand, innovation in areas like text messaging, and a renewed focus on service should mean plenty of customers stay put.

Cingular [Loss] 22 million Customer-service complaints have been an issue in the past; a system upgrade and popular features like letting customers roll over unused minutes may help retain users.

Nextel [Gain] 11.7 million Already 90% of its new customers come from competitors, and unique offerings like its Nationwide Direct Connect walkie-talkie service should draw more.

Sprint PCS [Loss] 18.8 million Hurting from a high customer-turnover rate, Sprint is still lobbying furiously against the FCC's and rival Verizon's public support of LNP.

T-Mobile [Even] 10.8 million Boasts the best new devices and a young customer base, but the strategy of offering extra-low prices and lenient credit requirements could end up hurting in the long run.

Verizon Wireless [Gain] 34.6 million Betting it can win new users, Verizon is pushing LNP and says it won't stick users with the bill for the $60 million system upgrade and new call center it says LNP will require.

FORTUNE CHART/SOURCES: YANKEE GROUP; MOBILE ECOSYSTEM; COMPANY DAT