Poor service

I had a loan with old mutual and my account has been handed over to landau attorneys ,so I am paying through them ,I got a message from old mutual saying there is an amount credited on my money account which were adjusted interest, I visited the branch they have ask for a bank statement so that they can deposit the money on my account which I did ,all of a sadden when I was home I received an e-mail saying it was a mistake there is no money to be refunded, I went back to the branch and they have made a call to where ever it was ,they told the consultant that since last year they never receive the payment for my loan ,and they had to put it there ,which came to my surprise cause from last year I am paying my account , so who the hell on earth gave them a permission to decide what they must do with my credit without consulting me??? first of all I am paying my account through their lawyers so now they I call for the explanation and ask for my money back I am being sent from pillar to post ,I would have understand if I am not paying my account I wasn't going to have a problem by not getting my credit.