Mtn retentions department bad service

I have been trying to cancel my contract with Mtn since 11 Aug 2021. All I want is for them to change no to prepaid and cancel the contract With no luck called hang on for an hour. Emailed no reply. Went on there website filled in a form. Went to Mtn shop they can’t help me. What do I do next ??♀️ that contract is R699