Cell C Robbing their Customers

I have recently discovered that after purchasing a daily data package, cell c continue to chow my anytime data while i still have daily data. I called their call center and i am told that background apps are to blame. This is a lame excuse because my daily data must be used by any app on my phone. Why dont background apps use the same daily data i purchased. This is one way cell c uses to rob their customers. Surely the decision to use which data package happens at network level. Sies Cell C.