It's not that bad of a thing to do, but if you decide to not use a primer, then the sanding is tremendously important. The surface has to be very dull and clean for the acrylic paint to stick well. You can test it by trying to remove some of the paint with your fingernails or apply some yellow tape to an area and pull it off to test the adhesion...inconspicuous areas of course. The only way to fix it is to remove the paint that is loosely adhered and then sand everything properly and repaint. You will very likely find that some of the paint is adhered and some is not....not very often is it a complete strip job. As far as painting with flat instead of a washable finish, most painters should know that is a bad idea. If you agreed on it, can you have them come back and apply the correct finish?

Thank you for the relevant feedback
Problem is no sanding was done.
Bid said prep and prime and stated flat paint, which was verbally corrected but not followed up on. I don't see much solution.