They will never stop taking your money

I had an account with these people and was always ahead of my payments. For the last debit order they deducted more than I owe them. When I call them for a refund they are sending me from pillar to post, asking for proof of payments and ridiculous stuff like that. How does your accounting system work? Or are you trying to **** money out of people. Please give me my money back before I go to the Ombudsman.