How to set data limit on androids.

Mobile data limit allows you to keep track of your data usage and also to know when
monthly data plan is almost exhausted. Set the limit through the following steps below :

    Go to Settings >> Data usage.
    Set your data limit by dragging the orange line to reflect your monthly quota.
    Set your data usage cycle based on when your "month" starts and ends, and you’re done.
    Data limit set
    Set Data Limit

You will get alert once your data usage reaches the limit you set.