Forced to stay on month to month contract because I refuse an upgrade

I took a phone contract (2 huawei Y72 )which was a take both for a certain amount in April 2024 which has ended on the 15th of this month,I called for a cancellation on the 18/03/2026 and I did a follow up on the cancellation for about 3 times to make sure it was done and I was promised that it would be cancelled after my last payment and before that I called a few times and I was refused cancellation cos they were forcing me to do an upgrade which I didn’t want and today I got a message that I have been put on month to month contract which was a surprise to me as they promised a cancellation,I called and asked why and a guy told me that on that contract they separated it and cancelled one sim and left the other one and which he said he doesn’t have an an answer for it,I asked for cancellation of the contract as I had one contract and was paying for one why separate the phones now when I have to cancel and no one even care to explain that to me they asked for both numbers when I was cancelling and I provided.so now I’m forced to be on month to month just because I refused an update I had one contract(two phones)and they made sure they separated the SIM cards so I’m left with something to pay since I didn’t upgrade MTN is a **** along with their workers