Vodacom insurance poor service

I've been trying to cancel cellphone insurance with Vodacom (that I never agreed on, and that they cannot show me a contract or proof that I took it), without success since beginning of February 2020. I'm still being charged for it. How do I get it cancelled? I have sent emails, and I gave spoken to operators. I've been assured that it has been cancelled, but it clearly has not been done.