People are being warned of a mobile phone trick which uses the name of BBC Radio Derby.
Listeners have contacted the station after being sent a text message which told them they had won £5,000.
The message gave them a number to call to claim the prize - it is a premium rate number and is nothing to do with the BBC.
Telephone watchdog Icstis said it was doing its best to close down companies operating such schemes.
One listener, Pam Bullocks from Alvaston, Derby, checked with BBC Radio Derby, but not until both she and her son had rung the bogus premium rate number and had been asked for their addresses.
Rob Dwight from Icstis said: "In the last few months it has become an all too familiar problem - simply, it's an out and out scam.
"We have come across a number of companies that have been leaving messages or ringing people up, telling them they have won a prize and asking them to ring an 090 number.
"The key thing to remember is that all 090 numbers are premium rate and should carry billing information.
"We have been working hard to shut these companies down."