MTN ******.

I have been getting calls from CSS for months now asking me to pay for an MTN account that I do not have. I have never even received a statement from MTN, but to get rid of the constant calls, I paid the amount quoted by CSS. I now require a paid-up letter from MTN as this is seriously affecting my credit score, and I can't seem to get anything out of MTN!! A bunch of ****** as far as I am concerned and no contact details to simply get me off their system!! This is linked to my ID number and I urgently require a paid-up letter but these don't seem to exist with MTN?! Not to mention, I have not had an MTN contract for years and when I left MTN I had my number ported and there was no outstanding balance. I wont even go there because MTN cannot even provide a statement with the 'supposed' amount outstanding that I paid. Will I ever be able to get a paid-up letter out of MTN??