How to unlink a site from the Pro chat plugin?

Hello,
I have two licenses for Social Chat Pro – Dev and Agency.

One site used by my Dev license is not valid anymore as they have moved out to other?hosts/agencies.

EXAMPLE:

Site A -> On Dev license, needs to be on Agency license… as they are moving away from us.

Site B -> On Agency license, changed to Dev license but did not free up the Agency license (site appears on both licenses).

Basically, I want to remove 1 site’s license — from Dev to Agency. And I need ONE free Agency license to do this.

Could you please guide me how to do this reassigning licenses perfectly? Or perform this from your backend? Many thanks!!