contract cancellation

Good day, i have 4 numbers with mtn, 072***4638, 060***4103, 060***3985 and ***. These 3 the contract is ending 072***4638, 060***4103, 060***3985. I was receiving airtime and and data. Recently i have received sms reading" Got this sms... Y'ello, your contract on +27***XX4638 is coming to an end on 2020-08-30. Your package price will increase from R77,39 to R179,88 per month. You can upgrade and save with MTN's unbelievable personalized deals. T&C's apply. #WeGoodTogether.To Opt out dial *135#. and i tried calling their callxcenter i held on for more than 20min and the fone would die. i have send emails, and inboxed them on facebook. i was promised that someone will call me with regards to cancelling my contract, upto thus day no one has called. only get those automatic replies.