Debit orders and poor service

I was double debited 27 November although papers were send from the branch a month in advance for head office to cancel one debit order. Till this point i havent received eny money back. Yet they tried to double debit my account yet again on 15 Desember. My account isnt in arrears. They just dont care i cant even pay my other responsabilitys it doesnt matter to them. I dont know what to do enymore.