MTN/Mondo agent ****!!!!!

I am being charged for a deal I did not agree to by MTN/Mondo on a Mecer deal I was told would be inclusive to my current deal of 80GB. I was told my currently monthly installment would increase from R360 to R439 and that, that would be my monthly amount and nothing MORE than that. December I get a shocking bill of close to R1k and I immediately alert them to this only to find that I am being charged R360 + R449 (which is not what I agreed to)- I informed them to listen to their recording and we are approaching one month and not one manager has contacted me to explain. I have requested they immediately cancel this nonsense and collect their device and they must note I will not be liable for any penalties asI have received another invoice today of over R1k- up until today no response has been given just ****** automated emails with useless reference numbers all the time. I, as the client continuously have to follow up with them as no one is willing to contact me - they even lapse on their turnaround time of 2 days to be in contact - this is really pathetic and I infact am considering jumping ship totally if this is how they treat long standing clients of theirs. This is messing with my credit rating which was perfect until this ****** nonsense came into my life. They might as well remove my number for any future deals. I want number further from them!!!