Poor Customer service with contract billing cancellation

I have now had enough of billing issues from Telkom .It's been 5 years since I gave 30 day notice to cancel my contract and go on prepaid.Now all of a sudden I get handed over to Nu debt management to collect R480 outstanding Telkom bill which I paid last month to get all this mess sorted.Now to my surprise I receive another Nu debt management owing amount of R190 and I wont budge until someone from billing can explain to me why there are these outstanding amounts and If there was a error from Telkoms side I would like a full refund from the previous collection.

Cellphone contract number in question:*** Account number:*** Client details: Sebastian Blignaut Contact Number:*** Email Address: ***