Contract not cancelled

I have 2 lines with Mtn and I requested an early termination for 1 line and was advised that I must pay R1166.98 to cancel the line, I made the payment on the 22nd of January and 2 days later I called to have my number converted to prepaid. I was told that it will be done within 4th ours, up until now it not done, I went to an mtn shop to find out what showing on my account and they told me that it shows that I have paid in advance.. I would like my contract to be terminated as soon as possible as I have paid in the full amount I was owing