MTN change of billing structure

After 14 years I want to cancel my MTN contract. I have always been a 30 customer, suddenly I was changed to pay as you use, but I was not informed of this. Suddenly I need to pay to get my account unsuspended. I have been struggling to get proper professional feedback since 7am yesterday morning. Its almost 12 the next day and my line is still suspended.

Surely it is not legal to change billing structures without the consumers agreement.

Horrific service!!