It doesn't matter what a "normal" patient load would be, that's unprofessional behavior.

Is the pain clinic part of a hospital ? Anyone in the community can request to talk to JCAHO (Joint Commission for the Accredidation of Hospitals and Organizations). I'm sure they would not consider getting back to you a week later, while you are in pain, to be a timely return of that phone call. You could also send a letter to administration at the hospital and make sure to fill out the survey that most facilities send out after any procedure.