Once you have purchased Mobile Proxies, you can create proxy traffic limits by logging into the Oxylabs dashboard and following these steps:
Select Usage Limits within the menu;
Click Create rule;
Select Mobile Proxies as the product;
Choose the proxy users that you want to limit;
Pick the period for limits (daily, monthly, or lifetime);
Set the traffic limit;
Click the Create limit rule to save your settings.
Additionally, you may choose what happens when the traffic limit is reached. You can select to receive email notifications and/or disable the proxy user altogether.
See this visual guide on how to set up proxy traffic limits: