Handed over with no notification

Good day, I currently have medical aid with Discovery, Last week I received a letter in the POST stating that i owe Discovery an amount of over two thousand Rand, dated 3 December 2015 - which is strange as i never saw any letter before stating that money is owed. The next day i got on the phone and called the call center to find out what the issue was and where the bill is coming from - The lady the explained that it was money owed to discovery by myself , Which is weird because I AM CURRENTLY A MEMBER OF THE SCHEME. She then also said that i have been handed over to be black listed - Which has now been done. The lady also continued to explain that NUMEROUS attempts have been made to contact me, Which i must have IGNORED RIGHT? The lady used one example she had on the system where some man contacted me - I stated that i was busy driving and asked that the man call back - I asked why he never called back : Oh Mam He sent you an SMS. Well, I must have been brain dead and deleted the SMS Along with ALL THE NUMEROUS attempts to contact me. How is this right to hand someone over and black list them if the have not been properly notified that they owe money. How ridiculous is this!!!