Deceptive marketing

I have a problem with Mtn, I have 2 sim cards, I was paying R319 total every month.In October last year someone called me to upgrade my data package and told me I will only pay R350 which was not a major increase.I took it.Same month I was billed R559 until now.I told them to cancel everything and put it back to R319 where it was.They are unable to do it.My account is in arrears because of the increase they made.I can't use the app to cancel the subscriptions they added as they suggested.I want them to cancel all the subscriptions so that I can pay what I owe.They were able to do the Changes but now they are unable to remove the changes.