Motorola has begun selling its Razr mobile phone in US stores again following a problem that caused calls to be cut off. 

T-Mobile and Cingular Wireless stores have started selling new batches of the phone, and Motorola is confident that the new shipments will be available throughout the US by the end of the week. 

The 'flip' Razr phones keep a call connected when they are open and hang up when they are flipped shut. However, the problem occurred because the phones were acting as if they were closed when they were still open, cutting off the call. 

Motorola said that only those phones sold by T-Mobile and Cingular were affected. Those sold at Verizon Wireless stores did not suffer from this problem because Verizon's network uses different wireless technology.