Calling Access level unsubscription upon certain events

I am trying to integrate Membership Pro in my own script, where I want to limit the number of file uploads per user. Having the basic structure laid down, I only need to call some plugin method to remove the user from a membership plan once he runs out of credits. So basically, a credit based subscription, instead of a date driven one.
Is there any callback url, or function I can use in my script, to remove a user from a specific access level? Say in my script, whenever a user uploads something, it checks the number of uploads since the last subscription, and removes him from the access level in case the maximum has been reached.

Thanks In advance!