Whats app Bundle

This is the worst experience iv had with Cell c. Iv been purchasing whats app bundles but every time it gets to 300MB it stops working. Whats worse is when i recharge with data bundles my whats app works fine. I have called customer care but no body seems know whats the problem, every agent keeps on telling me that "its a technical problem & technicians are working on it" the lies that you tell your staff. So please tell me if this matter cannot be resolved. I cant keep on deleting and reinstalling my whats app. its becoming frustrating. Please sort this sort. Iv never had such problems with any other network.