Is there a way to set up a provider so he cannot be double booked?

I need to either set up a provider so that he cannot be double booked for appointments, or restrict specific users from double booking…..yes it would be easier to fire the one doing the double booking when told not to, but until administration addresses it, I’ve been asked to set something up.  I’ve already restricted booking appointments in non-schedule slots (like lunch hours). 
Thanks!!