This is caused by apps update, data backup Gmail auto-sync and app notification. To effectively disallow this from happening, go to Settings > Data usage > tap the Option button ( either three vertical dots on the top right of the AG Chromr Selfi's screen of three stacked horizontal lines at the bottom of the screen > from the menu that pops up, tap "Restrict background data" and confirm. If succefully done, the will be a warning eclamation icon at the notification bar. Never click that notice as doing so will reanable background data transmission and you will have to go and disable it again under "Data usage". Let us know if you need any further assistance.