No one at Cell C branch can assist with data lost

Went to Cell C in East Rand Mall, Greenstone and Tygervally in CT. No one could assist. Even went to an iStore. Have a iphone 6. Data is switched of completely. Data is disappearing without using it. One minute you have a lot of data next minute I receive a sms to indicate low data left. Not using data for Whatsapp as I bought a Whatsapp data bundle. I cannot believe that everyone is so ***********. I have phone the Cell C customer service. No one can confirm what the problem is. They fwd me reference numbers and tell me that they will look into it but nothing has been done. In the meantime I'm paying so much on my account every month for internet data but not using it. I renewed my contract a few month ago with Cell C. What a mistake. I would love to cancel my contract with them.