Nobody can fix problems

I have tried for several months to fix contract issues with Cell C. I have 6GB of data on my account (as per web site service centre), but I cannot access any of it. I also have 300 min and 300 SMS's, but often get cut off in the middle of the month and told I have reached limits on account. CellC tell me their website is faulty, but never correct. Also, back office, front office, written communication office etc cannot talk to each other. Contract comes to and end now and will not renew. It is impossible to speak to the same person, and most times get hold of any person directly. Call centre is hugely problematic. They will call you back only when convenient to them, never at the time you request. Also, cannot produce contract or documents to substantiate what they tell you in the shop when you take out the contract.