BT is determined to recoup money lost as the result of a computer error which gave thousands of customers free access to the Internet for several months. A software fault in some of BT's telephone exchanges wrongly showed up 0845 numbers as 0800 ones. This led to customers of BT Internet services receiving no bills for access calls made from February through May of this year. Services affected include Tesco, WH Smith and handbag, all of which resell BT's wholesale Internet service. The telco giant is keen to play down initial reports that the sum it is demanding back is around £5m. "It is somewhere between 10,000 and 100,000 people who have been affected," said a BT spokesman, who declined to put a price on the gaffe. While BT admits blame, it will be pursuing those affected in order to get its money back. "Clearly it is our fault but obviously we still need to recoup the money," says a spokesman. Principal lawyer for the Consumers' Association Ajay Patel believes customers may have grounds for contesting this claim. "If customers didn't know BT was failing to charge them they may have a good argument," he says, urging affected customers to check the terms and conditions on their contracts. To have your say online click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.