Service sucks

I have 1 cell c account and it is endless problems, my wifi is supposed to be 20 gigs day and 20 gigs night. I have queried on a few times to prove that I get what I'm paying for however I never get proof. Now for the last few months they cut my account cause they say I haven't paid them however I have sent proof of payment. Today I call them again to ask to switch my account back on as I have made payment however they say I'm R850 outstanding but I have sent through proof of payment. I have reached my limit now with cell C. They just out to ***** from people