They are Havas' Arnold Worldwide, McLean, Va.;
Select Resources International, Santa Monica, Calif., is conducting the review. A decision is expected early February.
MDC's Fletcher Martin Ewing, Atlanta, was the incumbent.
The wireless carrier, with more than 5 million customers in Mississippi, the Alabama Gulf Coast, the Florida Panhandle, Southwest Tennessee and west Arkansas, faces challenges from more established carriers and also is expanding its network.