Complaint about Cell C

I'm getting sick and tired of this Cell C ****, last month I was charged R899 and they told me it's the insurance pro rata amount and the normal insurance amount including the old device amount. Then I was told that the following month I'll be paying for the new insurance and device which amounts to R788, now today I received an sms saying I'll be billed R961. 23, they are telling me that I'll be paying for the pro-rata amount of the device of which it's nonsense why didn't they tell me the day I received the new phone? I wanna cancel this damn contract and I'll be suing Cell C for being ****** I won't pay for something I don't know. I'm angry and taking this to the social media and let people see how cell c is treating their customers.. If I don't get this sorted by today I'm taking this to Twitter and Facebook trust me I will drag your name down because I've been a loyal cell c customer but cell c has never been a good service provider to me.