MTN terrible service

Signed up for a black Friday deal with mtn and upgraded that same line a few months later on another black Friday deal in november 2019 seeing the line is eligible for upgrade. I signed a 24 month contract for R259/m but recently noticed im being charged R359/m and they now say ooh its a “black Friday service fee”, I went through my documents i signed and no where does it say there will be a “fee” and premium will/can be adjusted, okay but i have signed a 24 month contract for R259/ month which means locked in for that price. I refused to pay the amount and they suspended my line. I could not make or receive calls, could not load Data or Airtime and could not sms. This is utterly ****tup Sorry for my language but MTN better do something about this