Few weeks ago had a MX passenger door latch failure that I tried calling for appt and never got through. Went on line and made an appt for about a week later, that was the earliest available. My wife got a confirmation email from them, and decided to email back, and they answered, and got us in earlier because the door was not operable. While I was in the service dropping her MX off, I made an appt for 4yr service for my MS, which was about 2 weeks out. After I dropped it off for that appt, they kept my MS for 1 week before they got all the work done.
So, at least a few weeks ago, they responded to email, maybe they aren't even doing that now. Going to Dedham itself and walk in to talk to them, if you can, is one option that should work.
I didn't mind them having my car for a week to get the service done, as I got a brand new MS loaner. They are now exclusively using Enterprise for loaners, but Enterprise has several Teslas in their fleet.