DMC
Paid up accounts still deducting from my account

Hi

I had 2 personal loans from FNB witch was handed over to DMC for collection.
DMC contacted me for payment arraingements witch we made and the money went off my account every month via debit order.
In March 2013 i asked for a settlement amount on both of my loans and paid it up.
At the biginning of march the debit orders ran again and they deducted the monies as usual. i phoned them to ask if they can mlease refund the monies as the accounts are settled. The could not tell me if they can refund the monnies. After sending them emails confirming settlement and waiting for a reply, i still havent heard anything from them.
Now in May 2013 they yet again debited the monies.
Please can someone tell me what i shoud do to get my money back and not be debited next mont again.