The FCC mandate that lets customers port wireless telephone numbers to any service provider is expected to go into effect today.Users are promised unprecedented flexibility and choice with this capability, which will cost the wireless service provider industry more than $1 billion when all is said and done, according to the Cellular Telecommunications Industry Association.Until this week, users had to forfeit their wireless telephone number if they wanted to switch providers. Now users in the top 100 markets must be allowed to take their numbers with them.Through a series of checks and balances, wireless and local service providers are working with a number of third-party providers to help facilitate the porting process. If all goes well, users should expect their numbers to be ported in about two-and-a-half hours from the time the process is initiated.Some carriers will support only porting requests during certain times of day. This means users will not have their numbers ported in a few hours from the time they request the switch, but a few hours from the time their new provider places their porting request.Wireless service providers are expected to support porting in the remaining markets throughout the U.S. by May 2004.Based on an FCC order that was issued earlier this month, service providers also are expected to support wireline-to-wireless local number portability beginning today. This will let users move their landline telephone numbers to their wireless carriers if they choose.