How do I disconnect VPN on my MacBook Air?

If your phone has a data plan, you could use it to search for that information online rather than your computer.

As a side note, you could also look for the VPN icon in your menu and either click it or right click it and see if it has disable option. Or go into your application folder and find the VPN app there and load it and look for disable. Most of them (if not all) have the ability to enable or disable at will.

The best thing to do is go to the VPN webpage from where you downloaded your VPN from. Then check their support page, community, or knowledge base for information on how to disable your VPN. Or even how to uninstall it.