Homechoice debt collector hounding me with calls and mails

I had an account with homechoice which I registered with debt review, and the debt review company was paying you monthly. When I cancelled I phoned and emailed Home choice so that I can continue paying but I was advised the account is paid off, I then asked for a paid up letter and it was send to me in 3 days. Now I've been receiving calls and mails from MBD debt collector telling me I'm owing R5000 which I fail to understand because I know very well that the account is paid off.