Paid up letter and terminating contract

I am so disappointed by MTN ,a big company that do note take their customers seriously I have been asking for a paid up letter since the 17th of April I was communicating with legal ,which they fail to assist me they told me they are allocating my payment till today ,I even went to gateway umhlanga was assisted by Leo she then logged a ticket but when I called the called centre I was told there was not attachments for my proof of payments .I wanted to close the contract and I wonder what is so difficult for them to lete know what is going one I Even sent a complain till today no one has responded I am so disappointed on MTN of the poor service they are giving to the customers .