I am so very sorry that you were bitten. I really feel your pain
My husband is a certified farrier and for a while he was doing some specialized shoe/trimming work. What really annoyed me most was that people didn't TRAIN their horses to behave with the farrier.
Like duh
I am sure that you experience this a lot. People bring their unmanageable dogs to the groomer to have nails clipped and ears trimmed and to have a general grooming done -- and they haven't put forth the effort to train the dog to behave properly and accept grooming. I know that there are exceptions - some dogs just are very difficult to work with, but geez, louise, they should at least warn you
I hope you charged them extra