Alastair Mowat, who imports musical instruments from his home in Huddersfield, West Yorkshire, discovered that someone giving his name and telephone number had called BT asking for his telephone to be disconnected.
BT failed to check that the request was genuine and cut off the line. It has since admitted the error and offered pounds 20 compensation. Mr Mowat believes he may have lost important orders because of the mistake.
Since the incident BT, which transfers or disconnects 1,000 lines a day, says it has improved its vetting procedures.
Mr Mowat returned to his home-cum-office on the evening of 17 August to find his telephone apparently out of order. When he reported it, BT told him that he had called the previous Friday asking for it to be cut off.
A 'Mr Mowat' had rung saying he was moving home and giving the telephone number, which he wanted moved to another address. 'BT said all that was needed to do this was to give a name, telephone number and address, which are easily obtainable,' Mr Mowat said.
Mr Mowat has demanded to know why BT did not ask for his account number - a reference which is provided on bills and customers' letters, but would only normally be known to account holders. BT could also check requests by asking for other details, or simply phone the caller back. The pounds 20 compensation was 'irrelevant', he added.
Michael Hepher, group managing director of BT, confirmed in a letter to Mr Mowat's MP, Graham Riddick, that the incident occurred. 'There was no reason to doubt the authenticity of the caller and we accepted the order from the details given during the conversation,' Mr Hepher said.
'Account numbers, being a comparatively recent addition to telephone bills, are not always remembered by customers and it is for this reason that we simply ask customers for their telephone number and address on an order.
'As a further safeguard against any problems we normally send a confirmation letter to customers in response to telephone orders, but I regret this was not done in Mr Mowat's case.'
Mr Mowat has no idea who impersonated him to ask BT to cut off the line. 'I was waiting for five faxes from Taiwan that day and only received two. The three I missed are not good for my reputation.'