MTN bullying refusing to stop giving me data despite expiry of contract

I had two contracts with MTN, each set to expire in two years. Upon the expiry of the contracts, I went to the Rosebank MTN store, where I had initially taken the phones to cancel the contracts. I was told the store does not handle cancellations. My understanding was that I did not even need to inform MTN to cease providing data and deducting money from my account once the contracts had expired. I made multiple calls to MTN to stop them from providing data, as I no longer had the lines for which the data was intended. Eventually, I managed to convince MTN to cancel the contract on September 30, 2022. To my surprise, they continued deducting money from my account. Frustrated, I decided to block them from accessing my account. Now, I'm alarmed to receive threatening emails from MTN, claiming I owe them money, despite having evidence that I called to cancel the contract on September 30, 2022. Since MTN records all calls, they should have a record of my cancellation request. Two weeks ago, I called them and was transferred between various offices for 2 hours and 39 minutes without any resolution. I also sent an email to the Roodepoort complaints department, but they chose not to respond, even though they acknowledged receiving my email. I feel MTN is treating me unfairly. It's perplexing that they continued providing me data when they realized I wasn't paying and are now attempting to pressure me into payment, which I find unjust.