Billing dispute/ Incorrect charges

I upgraded my contract on the 28th May 2018 with Telkom and was billed R1400+ on the 31st May 2018 however to my surprise im still being billed even after my contracts done. I've logged my dispute multiple times via your app, email, I called your call center and even went on Twitter and I am yet to get any feedback. Telkom Mobile consultants keep telling me that my contract is 15 months old because I cancelled something last year, my question is what and if so why was I continuously charge? I have all my invoices from my very first debit order so somebody was not updating my billing correctly. Their service is pathetic and its just a reminder of the first time I took a contract with Telkom where I got debited for a device I didnt have now im being charged repeatedly for a device I'm done paying. I want to be reimburse me for the incorrect charges and want somebody to get back to me regarding case number ***5