Legal fees added after settlement was paid.

I was behind on my RCS Game account due to unemployment for a few months. On the 11th of February 2016 my mother in law offered to settle my game account for me. i called MBD credit solutions (who handled my account at the time) on ***. I asked for a settlement on my game account and the lady on the other side gave me the amount of R16 450. The next day on the 12th i paid the amount of R16900 which was over and above what they gave me into their bank account. Then on the 15th i received an email from VVM Dept collectors informing me the case was handed over. i immediately called them and explained that the payment was already made on the 12th of Feb 2016 and even forwarded them proof of payment. Today on the 25th of feb 2016 i received yet another call from VVM dept collectors asking me for the amount of R790 that was added to my account after the settlement was given for legal fees. I told her the payment was made the day after the settlement was given to me. She just told me i have to pay them the R790 settlement before they can give me a \Paid up\" Letter. The settlement was given and i paid it. I am not paying a cent more than the settlement given. PLEASE ADVISE! "