Telephone operators yesterday warned users against a text message scam currently in circulation that tricks people into calling premium rate numbers.

Some mobile phone customers have been receiving text messages asking them to urgently call an 090 number. Having done so callers are then connected to a premium rate number charging £5 a minute, which simply sounds an engaged tone. A recorded message then advises customers to hang up and call again, hopefully conning people out of a further £5.

BT Cellnet first raised concerns after receiving a number of calls from worried customers who had been duped by the scam.

"This isn't the first time scammers have used premium rate lines to con people out of money," said a spokesperson at BT Cellnet. "We would just like to advise people to be aware of these scams and report any such message they receive to their operator."

But BT Cellnet is not the only company to be targeted, with Orange and Vodafone customers also receiving similar messages.

Telephone regulator Ictis (the Independent Committee for the Supervision of Standards of Telephone Information Services) confirmed it had already terminated four premium rate lines, but would not confirm which companies or individuals they belonged to.

"These scams are cruel and many people are caught by them," said a spokesperson at Ictis. "Of course any person suspected of partaking in such activities will find their line is shut very quickly, but apart from warning people to be vigilant there's not much else we can do."