PIC Freeze

PlC stands for "Primary Interexchange Carrier" and is synonymous with long distance carrier. 

LEC stand for "Local Exchange Carrier". LECs provide you with your local dial tone. (Usually a Baby Bell but it can be a local reseller of local service.) It is the local company that makes the switch from one PIC to another, not the long distance carrier.

PlC freeze

A PlC Freeze is a freeze on your long distance service placed with the LEC. It prevents the LEC from changing your long distance service, even though you have sent in an application or request to a long distance carrier to change the service.

Most of the time, the customer has asked for the freeze, but sometimes the existing long distance carrier does it to try to prevent the customer from switching. This is often done by sales people for the major carriers such as AT&T, MCI and Sprint, etc.

How to thaw the freeze

Call your LEC business office (number on your phone bill) and see if there is a PlC Freeze. If there is one, simply request that it be lifted. You can also ask them to change your long distance carrier, if you wish, although experience has shown that if you ask for more than one thing at a time, you don't get it. As such, it's better to call back the following day to request the switch of long distance carriers.