BestMed spamming for money

I cancelled my membership for many reasons, among which was that I had to pay thousands out of my own pocket for a simple gastroscopy. When I cancelled I was not made aware of any money that was due and now months later I am receiving statements telling me I owe them R816 and they will only stop spamming me once I settle in full (with newsletter and statements and all sorts of irrelevant nonsense) and the latest email wasn't even addressed to me, but to someone named: Mr Viera Costanho. I am not nor have I ever been a Mister. BestMed seems completely *********** and now is demanding money?