Bad treatment from cell c

have logged a complain and cell c promise to make a follow up on my situation and the only answer that I have received is that they have manage to allocated the payment that was made last year December and one of the consultant told me that I need to pay R826.96 instead of R600. When I asked the consultant about what is that money for she failed to answer me, on the following date I receive a message that I need to pay R1436.97, my monthly instalment is R600 and they have change that on the system that the monlty installment that I should pay is R678.49, that is not the amounth that I am paying I took a phone and the constract says I must pay R600, and the agreement date is 15th every months and they have also changed that to 18th without my concerned. And now I can not use my phone, they have closed it for the third time, this thing is draining me, I am tired of explaining one thing over and over to different consultant without any positive response, they are making a mistakes on their side and expect that I am the one that should suffer, they have failed to protect me as their client, I have been a loyal client to cell for quite too long I have never missed any payments and now I am a bad payer, my clear score has now have 3 red dots and I am under dept review of which that something has never happened before, they took me for granted, I was using capitec as my salary account and I now changed to Nedbank because I am loosing a lot of money through cell c, and I do make sure that I always a transfer of R600 for them to be able to make a debit order but they don't I only get messages that they were unable to debit on my account insuffient funds, on their side they want to take R678.99 instead of R600.