I've tried everything , how do I cancel my contract !?!

On the 10 March '23 I went into campus square MTN branch to request my contract be cancelled as I was informed since my contract was expiring I would automatically be debited R500 plus rand a month for the same contract I was paying R150 for .. as there was load shedding I was told to call the call centre .. tried calling the next day only to have an automated message saying closed for the weekend .. on Mon 13 I called and after nearly ages spend holding and being transferred I was told I had to give 30 days notice and since their billing goes thru o the 12th I'd be billed once again .. after being billed again in April I went back to campus square MTN to make sure it was the last charge .. I sat on the phone again for an hour and a half being transferred from pillar to post only to finally being assured it was the last payment .. it's May and I've just been billed again .. I'm at my wits end as to what else to do ! The thought of dealing with MTNs *********** and especially as far as the branch goes unwilling to help staff is giving me anxiety