Alltel, the wireless carrier with the largest geographic network in the U.S., wrongly claimed that Verizon customers must extend their contracts when they change calling plans, according to the false-advertising lawsuit filed Wednesday in federal court in Richmond, Va.

“Whatever merit this comparison may have to other carriers, in the case of Verizon Wireless, the supposed ‘advantage’ is pure fiction,” Verizon, based in Basking Ridge, N.J., alleged in the complaint.

In the disputed ads, mock Verizon sales representatives try to stop customers from switching to Little Rock, Ark.-based Alltel when they learn Alltel will let them change calling plans, including usage minutes and text messages, without extending their contracts.

Verizon said its customers have been able to change plans without extending their contracts since Oct. 1.