Payment complaint

My debit order with this business did not go off. I did pay through their secure online payment website. They keep sending me emails to pay my outstanding account which I did, I also provided them multiple times with the proof of payment as well as the refrence number for the payment and my account. They keep sending me emails to pay. I can never get through to accounts by calling. Now they are threathening me by wanting to cancel my membership. I have proof that I dont know how to publice here.