Advertisers on a Hampshire, England, equestrian website are being targeted by scammers who are trying to steal their credit card details.
Dozens of users of the New Forest Equestrian Directory (NFED) are receiving calls from criminals posing as site editor Steve Kitcher and asking for credit card numbers.
"They say there's a problem with their advert and ask for the details," said Steve. "We had a number of instances of it last year but, in the past few weeks, I have been contacted by dozens of my customers, asking if they have been scammed."
Mr Kitcher says he contacts his customers only by email and would be able to quote their agreed password.
"If you are concerned, hang up and contact me," he added.
Some advertisers have lost money to the scammers, but not Tina McDonald of New Milton, Hants, who is selling her daughter's pony through the website.
"A man with a Scottish accent phoned me yesterday saying my payment had not gone through," she told H&H. "I had my credit card in my hand and was going to give him my number, but when I asked him for my password he said it was confidential, which rang an alarm in my mind. I was very lucky not to be taken in."
The Hampshire Police Force is investigating the matter.