Unhappy customer

I am not happy with MTN with regards to my 36 Months contract, I am having 3 numbers with MTN and all of them are on contact, one of those numbers 36 months contract has come to an end I did notify them on 16/10/25 they told me it will run until 11/11/25 I don't have a problem with that, now I owning MTN R3000 in less than 15 days when I ask them no one is giving a clear answer. I went to MTN Chris Hani kiosk counter their system was down, then I went to MTN Brentwood park they couldn't tell me what is your, then we call MTN 135 number they told me because I was late to notify them so they are charging me for that, when I ask them contact ends on month 36, MTN says they will continue to month number 37 so they are charging me for that. When I was taking a contract 3 year back it was never explained to me and I was told that my contact will run for 36 months after 36 months I need to decide whether I continue or not now MTN says I must pay R3000 I am not going to pay that our money until I understand.