First thing's first:
1. Was the shop accepted and do you expect to be paid?
2. Will this shop affect your overall rating where it'll hold you back from certain privileges such as self-assigning, signing up for jobs requiring a minimum rating of __?
If yes to #1 and no to #2 to the above, I'd just bite the bullet and move on.
If it's the opposite, I'd explain the situation in detail once more and how it would affect your experience with the MSC by not finding a middle ground. See what response that'll get. If no response or the situation doesn't get any better, I'd take up to the next level and contact someone above the scheduler's authority. Of course, this will also depend on how important this MSC and their clients are to you as well.
Shopping the Greater Denver Area, Colorado Springs and in-between in Colorado. 33 year old male and willing to travel!