Oh, I'm so sorry Gizmo is hurt. I'm sure that was awful for him, poor fella.
Let me tell you, that vet would have heard what I had to say before I left and there would be not doubt that I was not paying. I would have directed him to see his on site groomer if he expected to be paid.
I would certainly call above this vet if possible, at least the owner would know how business is being conducted.
Good Luck...Hugs ))) to Gizmo