Refund

I took a 24 month contract with Mtn and on the 24th month I called in to cancel my contract which was retainer department. They informed me that my last will be in February 2023 and the amount debited will be prorated. They billed me R1145 instead of the prorated amount and my normal subscription is R209 a month. I called customer care so many times but nobody is helpful. I get put on hold and while holding, the call drops then I have call again, hold, speak to someone, get put on hold again and call gets dropped again. I want my refund.