Can we ban or block specific customers from signing up?

Unfortunately, Recurly does not currently offer any support for banning signups or purchases on our end. In these cases, we normally recommend tracking the customer IP addresses on your backend then banning the IP address from accessing your site. Additionally, if you see a specific set of billing information being used and you would like to refuse service, you can check in with your payment gateway and have them block any transactions processed for a specific customer or set of billing information.