Ofcom has warned broadband firms TalkTalk and Tiscali that they face severe consequences if they do not stop charging people for services that had already been cancelled.
The telecom regulator issued a warning to the two companies after it was found that they had been harassing customers by continuing to demand payment for services that had been already terminated.
Ofcom said that it had received complaints from 1,000 TalkTalk customers, but said thousands more may have been affected.
TalkTalk has blamed a new billing system that was installed after it bought Tiscali in June 2009.
According to BBC News, the two companies have been given until December 2nd to resolve the issue or face a 10 per cent fine of their annual turnover.
Ofcom's director of consumer affairs, Claudio Pollack, commented: “Our investigation into TalkTalk and Tiscali UK found that they had billed customers for cancelled services; this is unacceptable which is why we have ordered them to clean up their act or face the consequences.”