For a contract that was meant to expire. I'm still being billed and about to be blacklisted

I took out a contract a few years ago and this was renewed twice. Eventually this was not renewed and was meant to be cancelled. For some reason I was still debited monthly for this and eventually when my credit card changed. And I finally tried to get in contact with you. All emails went unanswered and now about to blacklisted for a contract I was not even meant to be billed for.