Skype for Business 2015, disable users that don't exist in AD

Question

I have 4 users that are in my Skype environment that point to accounts no longer in our domain. I'm unable to disable them\ because it can't locate them on the DC to remove them. I've heard of ways you can do this on the database side, but wasn't exactly sure the route. I did try updating my user database and still having the same issue. Problem is, these users are in my old Skype Pool that I need to remove, but I can't remove it while there are users in it.