REPEATED ABUSE BY MTN. WHY IS MTN SUCH A ***ARD AND A GREEDY BULLY?

I had a contract that I was supposed to upgrade three months ago. When consultants were calling me, I informed them that I wanted to cancel. They informed me to call on the 15th May 2025 to give notice, which I did because the contract was ending in June 2025. I told them that I would like to retain my number and should be converted to prepaid.I came with the number to MTN by porting it almost a decade ago. A week later, I called again just to ensure that my request was recorded, which was done and I was so happy that I didn't have to pay anything to MTN again.Nothing was mentioned about the device cancelation fee by the two consultants from the MTN customer care line. On the 20th June 2025, I received an email stating that I had to pay R1 159 for device cancelation. I had a fixed-term three year contract coming to an end. Why am I treated as if I was renting and I was breaching the contract? The value of the device has depreciated. Why am I being penalized or held at ransom by MTN. I feel bul**** and abused as this is not the first bad incident that I have with this giant network service provider? I need your assistance