Hello Leo,

Thank you for your interest in our product.

You can do the following: You can ask for a mandatory deposit when creating a meeting so that even if they cancel you get part or all of the money. 

You can add a membership plugin on your site, and enable "Automatically create Amelia Customer user" in Amelia Settings/Roles. Then, when they book, they will be linked with the member role. 

After they book and cancel, you can block access to your site to specific members. That doesn't prevent them, though, from booking with another email address and details, so you may want to look for something that blocks the IP address. Unfortunately, we're not aware of a plugin like that.