FCC Probing AT&T; Cell Switching Problems

Federal regulators sent AT&T; Wireless Services Inc. a strongly worded letter seeking information about difficulties the company appears to face in assisting customers who want to switch cellphone service to rival carriers.

Retailers and consumer groups have complained that technical problems at AT&T; Wireless have prevented customers from taking advantage of new Federal Communications Commission rules that allow cellphone users to keep their phone number when switching carriers.

John B. Muleta, chief of the FCC’s Wireless Telecommunications Bureau, noted in his letter that the FCC had “received a number of complaints.”

Muleta set a Wednesday deadline for the company to respond.