Free accounts will revert to the most basic plan, which has just 2GB of data per month, Pro accounts will not.

Why is it like this?

Normally we provide 2GB of data to free users. The reason why we give 10GB when you provide a confirmed email address is so we can send you Windscribe related promotional emails and try to convert you to a Pro user, since we're a business and that's the only way we can pay for servers and staff salaries. If you don't wish to upgrade, and don't want to receive our emails (0-2 per month), you can use the basic 2GB account.