AT&T, the largest wireless U.S. carrier, said it will be selling its service through Wireless Advocates, which sells wireless phones exclusively in Costcos.

AT&T phones will now be sold in nearly 370 Costco locations nationwide, reaching 35 million Costco cardholders.

Wireless Advocates is a Seattle-based company and is a division of the Car Toys enterprise, which also sells wireless phones.

It also offers service from Verizon Wireless and T-Mobile USA

"Costco is near the top among retail outlets in mobile phone activations, so we are positioned to better deliver the benefits of wireless services to a larger group of consumers. Partnering with Wireless Advocates will ensure that our products are sold with care and expertise and that customer service will be a top priority," said Glenn Lurie, president of national distribution in AT&T's wireless division.

The Costco kiosks will sell such phones as the Samsung A437 and A517, as well as Nokia and Motorola models. The Samsung BlackJack will also be sold in select locations.

"The demand for wireless services in Costco stores continues to grow," said Wireless Advocates CEO Dan Brettler.