DOUBLE DEDUCTIONS -MANAGER UNWILLING TO RESOLVE

I went to the shop yesterday because they had double debited on my bank card when i only used my card to purchase once. I asked to speak to manager and when eventually we talked,he was not helpful, he did not want to look at the bank statement that i had as proof of their deductions. He was rude, did not even want to check his records, when i asked him for his details as the manager he refused and said what do i want to do with his details, while i was talking to him he kept on moving away from me and telling me that i wont get help from him, i must speak to my bank. Even thou i explained that before coming to the shop i called my bank and one of the franchise for advise he still dismissed me and did not show any interest to resolve my issue.