FNB scheme

I would like to complain about a loan I took in December which was a short term loan which last payment was supposed to be in June but I been changed service fee and interest even when the term is finished. I went to the bank today at Protea Gardens mall the first agent couldn't explain why. I called loans department spoke with Vuyokazi Msweli she keep on saying I am owing service fee for June which to my knowledge has been paid and she was rude and didn't give me a chance to speak. I then spoke to agent number 2 in the bank thinking he will be able to explain better he then said his aware of this thing that loans department does and he doesn't know why it's done it's a deliberate thing I must just pay that service fee and all will be done. I can't just let it go I want my money back all the extra service fees and interest you have been taking I WANT IT back into my account..