i've been handed by Mtn

I took a contract phone with Nashua mobile in 2013 before it was liquidated and handed over its clients to MTN. I therefore went to an MTN store to enquiry about the status of my account because I wanted to pay it off as the contract was ending on the 19th of March 2015. I've made a double payment of R818 in February because I was told that was the amount I had to pay before the contract it's terminated. To my demise I get an sms that I had an outstanding fee of R59 in April 2015. I then went to an MTN store to pay of the R59 on the 15 of April. Now this was the cream of the crop on top of all the payments I've made I was then told that I owed another R400 and some change which I don't know where does it come from, and why I'm I still billed for a contract that already ended in March 2015. I've made several calls and enquiries and I wasn't getting the same information whenever I spoke to the call centre agent or even the consultants at the stores. Req.*** Nompumelelo responsponded on the 15 october 2015, that the matter has been escaleted for assistance but now the account has been handed over for debt collection.