Impossible to cancel membership

When looking for a medical aid I approached Bonitas first and I received such bad service and an even worse quote so I went with another provider.

Low and behold - I've just learned that Bonitas hasn't cancelled my membership and I'm still expected to pay them for a plan that will only start in 3 months - a plan I never actually agreed to.

I've contacted their call centre and had the phone "accidentally" dropped on me 3 times after I explained my situation. The fourth time the operator was trying to give me an email to send my complaint to, but then spelt the email differently every time I asked her to repeat herself because I got the feeling she was being intentionally unclear.

Lunacy.

All I want to do is cancel my membership that I never agreed to in the first place.