On our credit card statement a few months ago we were charged £154 for a transaction we knew nothing about. We weren’t able to trace the firm and when we queried the charge the money was credited to our account, but the same thing has happened every month since.
Your credit card firm has been very slow off the mark. It shouldn’t be difficult to find out who is debiting your account, since the credit card facility used by the retailer will have a code making them instantly traceable via their bank, ask for an explanation in writing. Although there is obviously a risk of abuse of the credit card system, particularly over-the-phone credit transactions, the Consumer Credit Act gives you reasonable protection from loss as long as you haven’t authorised the transaction concerned or allowed someone else to use your card.