Businesses across the UK have reported a rise in so-called "friendly fraud", or chargeback scams, where customers tell their credit card companies they haven't made the purchase listed on their statement, but in fact, they have.
The customer receives a refund, and the seller is charged the same amount - plus an additional fee for the process.
One business owner in London said he was so frustrated by the impact it was having, that he started investigating the fraudulent claims himself.
A spokesperson for UK Finance, which represents the banking industry, said: "Chargebacks are an important consumer protection. Unfortunately, there are cases where consumers make false claims."
Rusty Nart owns Green Monkey London, a cafe in Tooting, south London, and Fingers Kebab shop, in New Addington, also in south London.
