If your phone does not have unlimited mobile data plan or Wi-Fi network you are connected to the data Just be careful you do use.
If you spent more data out of the data plan you may need so costly.
Android for mobile data limit, you can decide which app a month how much data can be used. Just watch videos or use the data to spend time on Facebook can not grow.
The data service on a variety of programs because of living continue running in the background, such as GPS or email.