Bad service

I have been struggling to get a clearance letter from Markhams head office. I have been contacting them since I found out that they got me listed claiming that I owe them ,when asked how much do i owe them the answer I'm getting is that my account doesn't show any oustanding balance i have been calling them since February to try and get the confirmation letter from them that I was clear so that I can clear my credit record. I have been continuously being promised that the letter will be emailed to me and until now I'm still waiting.

Please help I need to clear my credit record. My contact number *** Email *** or ***