Dishonesty

I took a loan last year January 2019 and I skipped one month which led my account to be in areas but on the next month I paid the outstanding amount and was never again in areas. On August I wanted to settle the entire amount I called wonga loans how much is outstanding they said its 1049.60 Indeed I paid the amount and sent proof of payment immediately. One month passed, in October I received a call from wonga loans demanding another payment I questioned it and I was told to resend proof of payment I did that via an email and asked if they could at least reply to say they've received the documents, November and December they called and I paid the amount they said I'm owing which was R146 something and R200 for December, again got a call January to pay I told them now I ain't paying any money that I do not know especially when they do not bother replying to emails. My credit score has dropped immensely and I can't open any accounts due to such inconvenience and unfair treatment