I have a problem with an iphone 6. It is practically unusable. If i interact with the screen, changing screens, holding the screen to go into app delete mode, or open more than 2 apps. it freezes completely. I formatted the phone and started afresh, keeping only my whatsapp chats, icloud and photos. I downloaded an app to check the usage of the phone, the memory is constantly full The phone is a 16gb config with 4-5 still free. Whats up? Its still under warranty.