Small business owners have been warned about a telephone scam offering cheap or heavily discounted advertising in local newspapers and magazines. Devon and Cornwall Police say scammers have targeted at least three firms in North Devon during the last week. Each time, regular advertisers were offered discounted advertising space in a sister publication and asked for credit card details over the phone. Detective Inspector Praveen Naidoo said: In one case, a business agreed to place a £20 advert but scammers attempted to bill the firm for £3,500. Thankfully, this was declined by the card operator, who phoned the client to check whether they had authorised the transaction. They had a lucky escape as three further transactions of £1,000 were also declined; other targets may not be so fortunate. Police launched Operation Jessica in January last year as part of a bid to crack down on fraud and cyber crime. DI Naidoo said: Fraud prevention is all about awareness. Be suspicious of any unsolicited call from someone requesting bank or other financial details; if youre not sure, end the call and telephone a trusted number. Never give your PIN, security or bank details to anyone over the phone. And remember, if someone offers you a deal that sounds too good to be true, it probably is. Victims are advised to report incidents to Action Fraud on 0300 123 2040 or visit Action Fraud by clicking here.