*****ing my money

I have trying to deal with Cell since beginning Jan 2018, I have a straight up 100 contract so my monthly billing is R209 (been that way for years and years) recently I have been getting bills for R450 and R350, when I queried it they said that in July 2017 my account was changed to open line with a max of R400 ( I have sent 13 emails requesting the recording or proof of this change on my bill) NOTHING....... I cancelled my contract now and even with that can't get a confirmation that this has been done, I have been with Cell c for so many years, my new bill shows minutes and data billed, even though I am supposed to be on a fixed package. No use phone cell c anymore, each time you get a new person and have to explain the same story over and over again.