MTN won't let me port my number

I have been on a month to month contract for years. Did the calculations and asked to be moved onto prepaid months ago. Rather than doing that, I was moved onto a MyMTNZero contract. Now that I am trying to port my number, I get 4 different reasons why I cannot move to prepaid which are all lies. My number is being held hostage to make sure that I cannot move to another provider.

This is my first port of call. Next stop will be the ombudsman.