Poor customer service

I had a contract with MTN and it was expiring on Jan, in Jan I went to MTN to cancel the contract cause I was not interested in upgrading.

Now in Feb they closed my phone saying I still owe the R 976, why caused I paid that in Jan and asked the consultant at the Glen Mall to cancel, I should only pay for the tablet and to convert my phone to Prepaid and she confirmed she did.

This morning I recieved an sms indicating I now owe them R 1 783