Why is this icon (2 upward arrows in an triangular shape) appeared and how to remove it?

[Android Central Question]

When using the hand phone overseas, the icon ...an 2 upward arrows in a triangular shape appeared. Not sure what should be done or to remove it.

 

[chanchan05]

Data saver function to prevent you using too much data. You can turn it off in settings but your data usage, and your bill will increase.