Lesson learned for TS. From now on, go to setting and turn off data usage for apps that can consume a lot of data, eg. app store. It really helps to control data usage.

My ownself I only allow usage for Whatsapp, FB Messenger, cinema apps, Airasia and Safari.

Gotta be brain smart on certain things for example, beware on Whatsapp as although texting consumes very negligible amount of data, videos/photos sent by your contacts can potentially consume a lot if you're downloading them on data. In Whatsapp, best to disable auto download features.

Yeap, doing all these, tak susah mah. Easy only.