UNHAPPY CLIENT WITH MTN CONTRACT

I took MTN contract (phone Bach in 2021), Last month I caller to serve that cancelation notice they told me that I need to do it in September. When I called them now I am told that I'm late I should have 30 days before. On top of that the SMS that I got say something else. Please fix this issue, I cannot pay for another month while is not my fault. The consultants are treating us bad