What risks are there to leave mobile network on all the time

[android jack]

So I recently just left my phone somewhere but it wasn't until it came near our wifi that I can locate it. Since I have limited data I refrain from turning it on, for emergency only. So what are the risks, will it use data while idle?

 

[Aquila]

It can, depending on app and device settings. If you're careful to make sure the Play Store is only updating on WiFi, photos backup only on WiFi, social media sync is manual, etc. then it should be minimal amounts.