Impossible to cancel with Vodacom

I immigrated to the UK earlier this year. Paid my early cancellation penalty fee with Vodacom in December 2017 after which my contract was still not cancelled. I cancelled again in February 2018. They ensured me my account was cancelled but I still got billed R800 in July. I am feeling so hopeless. Will I forever get billed by Vodacom for services not used and a contract that was paid up and cancelled more than once? Vodacom. I beg you. Please stop billing me!!!!!!!!!!!!!!!!! What else must I do to get you to cancel me and leave me alone?