EDD-Customer-Role-Manager
Easy Digital Downloads Customer Role Manager
By default Easy Digital Downloads creates new user on checkout as a default user role subscriber. If your store has free products as well as premium products, you may want to have different user role depending upon the purchase amount of checkout.
Well, this is a simple plugin for doing that. When you active this plugin you will get two new user roles. Free Customer and Premium Customer. When your customer will buy any free product they will get role free customer and if they buy any premium product which price is greater than zero user will get premium customer role.
Then you can do anything with those roles, maybe you can allow premium users for getting support.