Wal-Mart is expanding its prepaid wireless service Straight Talk to include new phones that will work on AT&T’s network.

Straight Talk, operated by TracFone,  currently resells Verizon Wireless service.  Adding AT&T coverage expands service into parts of the country where Verizon signals don’t make it.  AT&T’s network reaches larger parts of states like Wisconsin, West Virginia, and New Mexico than Verizon does.

Straight Talk phones that currently work with Verizon are not interchangeable with AT&T service, however.  Verizon uses the CDMA standard for its network, while AT&T uses GSM.  The two are not compatible.

Wal-Mart’s prepaid service is appealing to consumers who do not require the latest handsets and seek wireless service without a two year contract or expensive add-ons.  Straight Talk delivers cheaper cell service than Verizon does, with both using Verizon’s network.  The same will be true as AT&T service is added.

Straight Talk currently offers two service plans

Wholesale wireless service, typically sold to prepaid providers, delivers enhanced profits to big carriers like Verizon and AT&T without having to spend money on customer support.  Many prepaid providers sell older, more basic handset models that may have been in excess supply, are reconditioned/used, or are inexpensive to provide consumers.