Contract not converted to Prepaid

Good day,<br> <br> I have made numerous calls to MTN and i have emailed them requesting them to convert my contract to prepaid effective 30.05.2015 as that is when the contract expired but to date my number is still on contract and I have signed the termination of contract letter and forward same to MTN and still no response.<br> <br> further to that they have increase my contract billing amount but i am on a top up contract of R199 and R259 respectively but my bill has come out to R400 and R350 respectively.<br> <br> I would like to finalize this matter as soon as possible.<br> <br> Regards<br> Laurey