Insurance enquiry

I upgraded my phone in Jan 2021 signed a waiver that I roll not be taking their insurance. To my surprise in September I'm debited an additional amount to the one I'm used to.called Mtn I'm told it's for insurance...HOW because I didn't take or accept any insurance I'm told it's the system..

I've called and sent emails with attachments and I've been debited again no one is getting back to me or rather has an answer but they gave an answer to debating my account..diribg calls I'm told to hang on till it hangs up.. all I need is a way forward to thus matter.