Sprint is targetting Verizon Communications and AT&T with a promise to cut customer bills in half for those that switch from its larger rivals. Verizon and AT&T customers who provide a copy of their bill at Sprint stores starting Dec. 5 will be offered a gift card for as much as $350 to cover phone costs and early termination penalties if they leave their carrier. They will then be matched with a similar service plan from Sprint for half the price.

Sprint is trying to end more than seven years of customer losses at the struggling No. 3 U.S. carrier.

Customers of fourth-ranked T-Mobile US and existing Sprint users are not eligible for the half-price offer. The new plan, which is a limited-time promotion, builds on Sprint's earlier offer to double the data allotment of other carriers for the same price.