Android devices are well known to consume much internet data compared to other devices, the problem majorly is when your device consumes data and you cant really identify which application is consuming much data, because there are a lot of background applications that access your internet.
LostNet Firewall: This is a great app that helps you manage apps and how they get online. It has options to block an app totally or to allow it have access to the internet only when on WIFI, you can also set geolocation accessibility and doesn’t require root access.
Android Firewall:
This is a folk of the popular application Droidwall that uses iptables to limit data usage and add security to Android but was discontinued, this works great too but root access is required.
AFWall+ (Android Firewall +): AFWall is another app in that category which tries to replace the discontinued Droidwall . Although no much success story but still does what it suppose to do but note that this process requires you root your device.
Go to Google Store and download any of these free applications.
Enjoy!