Never take a contract or any service from them!!!

I’ve taken out a contract with mtn and it was the worst financial, emotional and critical decision I’ve ever made. I’ve made all my payments and then they had the nerve to say I owe them for 2 months and regardless of me providing them with POP they just ignored the fact that I’ve provided the necessary proof of payments. I’ve been running around from store to store, email to email, phone call to phone call and up until today they can’t assist me. I’ve sent multiple emails and called multiple times again and still no assistance. I’ve been trying to get assistance with my matter since last year August and up until today they haven’t responded to my emails. My credit score has been going down hill from 621 to 586 and they still not getting back to me. They literally ruining my financial history and I can’t evens apply for anything. They should be canceled and their license should be provoked.