Blacklisting without sending any correspondence

Discovery Health just sent me a letter confirming that I have been reported to the Credit Bureau for an outstanding amount of R329.00. I have received no previous correspondence from then except for a very cryptic sms. When I phoned them they confirmed that there was no outstanding amount (proof of follow-up e-mail from them). Now, a month later, without receiving any written correspondence on the matter they blacklist me for R329.00. This despite the fact that I have a credit card with them with R95 500.00 credit available to me. I also have a life policy with Discovery. This is shocking and I will refer the matter to the Ombud as well as Financial Services Board - this is certainly not treating their customers fairly. I am also in the process of setting up a new practice and issues with my credit can seriously hamper my new venture and damage me financially. I handed to matter over to my lawyer who prepared the correspondence. This is truly shocking.