My data is finished again

I get a Data bundle from Cell C of 2gigs free and for some reason on verious months they send me an SMS mentioning that it is over. Now I have put this complaint to them before and I find it unacceptable that this SMS is being sent to me. I have an iphone4 which indicates to me that I have only used a specific overall data usage of 343mb which was date back to the 5th July 2015. This is the date my stats we're reset which indicates that my usage is way under the allocated usage given to me. Due to the fact that I connect to a wifi zone both at work and at home and make certain that my wifi is connected, I really cannot understand why my usage is high. Cell C, sort this out please, I have had enough. I understand that your corporation is big and mistakes happen but now, I need feedback! From a very concerned client that believes that this is not the first time it has happened to me but others...