MTN unfair rate escalation and USELESS/IMPOSSIBLE cancellation function

I have a MyMTN 30Gig data contract. My normal monthly subscription was R300. I was informed that my contract expired 25 Nov 2020 and with a huge SHOCK discovered that my new bill for Dec 2020 will be R2000 since the "special rates of my contract no longer apply". This is almost a 660% increase! INSANE!! I therefor had no other choice but to cancel the contract and this is where my frustration kicks in. I find it impossible to cancel a MTN contract. I have been phoning the retention department and after sitting almost 150 minutes on the phone altogether, no success. It is impossible to get through to them. I emailed them, I emailed the complaints department, NOTHING!! If you are considering MTN as your mobile network, think again, if you are in you are in! No getting out! This is unacceptable and you cannot get any form of service from any MTN department!