Whyzer has three plans: Free, Premium, and Elite. The upgrade page lays out what each one includes and what it costs.
What the plans change
Two things mainly. Feature access, where the MCP server needs Elite or a team. And volume, where each plan carries different monthly allowances for the things that cost real compute: dossiers, podcasts, and companies. See Usage and limits for the detail.
Upgrading
Upgrades go through Stripe from the upgrade page. Access changes as soon as the payment goes through, so you don't need to sign out and back in.
Cancelling
Cancelling is a request rather than an instant switch. You submit it from your account, and someone on the Whyzer side processes it. That means there can be a short gap between asking and it taking effect, and it's worth cancelling a little before a renewal date rather than on it.
If you're cancelling because a limit is in your way rather than because the product isn't working, say so in the request. Limits are adjustable in ways plan changes aren't always.