I want my paid-up letter

Very poor service, I have paid up my Mr. Price account that was handed over to them and I've been calling to ask for my paid up letter and now I'm being sent a statement that have outstanding of them charging telephone so every time I call them they charge me money, no one told me and explain how things work, when I call for explanation they drop my calls without explaining to me what's going on each and every call I'm told different shocking stories. I was told my account is paid up I must wait for 21 day they will send me the paid-up letter and I did wait 21 days pass I call again and I was referred to another person that deals with paid up letters and I call the person and she told me my account is still having lots of problems they will get back to me when I ask what kind of problems cause I paid all the money they wanted and my call was dropped .