Mtn sucks

I had contract with mtn in 2018 I was paying them very nice monthly then in 2019 I decided to pay settlement amount of R8700 fine, last year they got back to me saying that I owe them R6000 but all along they were quiet when I go to the store they say they can’t help my credit score is bad because of them I pay my debts very well but cause of mtn I can’t take credit anymore their lawyers I sent them proof of payment and all but they couldn’t help also now I’m sick and tired of mtn I will never let anyone in my family close friends or Colleauge take contract with mtn