I regret doing business with MTN

My contract with MTN was due to expire on the 10th of October 2020. In July, I had already contacted MTN to advise them that I wish to switch over to prepaid once the contract term is up. So in October, I speak to them again and they advise that I will be switched over to prepaid at the end of the month. It is now February 2021. I received an email stating that I need to pay them R1029.50 for my account. This is after I have spoken to Xolani, Neo, Mzwandile, Nosipho, Phumla, Sunday who all promised that they will assist in sorting this matter out. I am so sick and tired of MTN's empty promises and a business like this should be held accountable for how they treat their customers.