While I often have fun "acting" my scenario, I, too, have trouble "thinking on my feet" when the unexpected comes up. And even asking questions of the MSC beforehand, you can't come up with questions to cover every eventuality.
I'll never forget the time I drove 100 miles to see a banker. The guidelines SPECIFICALLY said to NOT call and make an appointment. When I got there, the teller told me bankers are available ONLY by appointment, and that I needed to go away and call in and make the appointment!
The next available appointment was two days away. Not doable. Took several rounds to convince the MSC they should pay me, as I performed MY part of the contract.
The MSC did pay me (and threw in a lovely, unexpected bonus!) AND rewrote the guidelines. Rewriting the guidelines made me feel appreciated; but who knows, maybe hundreds of other shoppers ran into the same thing. I'll never know, LOL!!!