Lies about contract and incompetant staff

I have had contracts with cell c for about 5 years. Last year i took one in my own name of R199 per month fixed fee. In february they decided to increase my fee with R9 per month without notifying me. When they finally notified me about this it was 3months later and they were about to switch off my phone. I phoned the accounts department every day for 5 days and all i was told by a very rude woman was she can't do anything i must phone her when my phone is off. I spoke to the financial manager as well as the area manager forKrugersdorp and they both promised to sort it out and phone me back but to this day I have not heard from either of them and they switched my phone off regardless. Now I pay my account the first of every month and after the 15 I receive weekly sms messages that my accounts are in arrears even though I have cell cCradlesone mall fax my proof of payment to accounts as soon as it is made. Cell c advertises on the radio they guarantee a fixed rate for two years so how can they increase my fee every month without informing me.