Repaid loan only to be told its not paid

I made a loan last year with Wonga and failed to pay the account the following month. However the month subsequent to that they were able to debit my account the outstanding amount and the interest that was charged. I then started recieving calls that my account was not paid. Despite sending my bankstatement as proof of payment and wasting airtime trying to rectify this problem, it still has not been resolved a year later. Instead i get rude consultants who are unwilling to use their logic. Im tired of calling you guys back and forth and requesting proof from you guys and being told that the money that was debited from my account went to another company and not wonga??!! That, according to me has nothing to do with me! I got debited the amount owing finished! I am not going to allow for my credit record to be permanently damaged because of this. Please respond to my complaint s possible as ive tried so many other avenues to get this resolved.