MTN is holding me at ransom

My contract expired in December 2024, and I opted not to upgrade due to poor customer service received. MTN has been charging me monthly post contract expiry. I was told that it is a requirement to still send cancellation even though the contract has expired. I did send a cancellation, and I was told that I am now on prepaid. A week ago, I tried to port my number elsewhere, but I was told MTN is preventing the number porting. I went to the Centurion branch on 12 March and spent more than an hour there without any resolution. The comms attached are from the agent who tried to assist but failed. I was told that there was an outstanding balance, but a few minutes later, I received a communication attached stating that there was no outstanding balance. I want to port my number, but MTN is preventing me