Please do us all a favor and report those rude Dining car attendants to Amtrak. Hopefully, others will chime in with the best and most effective methods of doing so. IIRC, emails and phone calls are not two of them.
I'd also add complements and contrast the pleasantness of those on the other two trains.
And be specific as you can be - down to their names if possible.
If you cannot call to complain or email to complain, how do you complain after the fact? I noticed someone else stated that they spoke with the conductor, but if you don't say anything immediately, and the first two options are out, according to your claim, does one have to write a formal letter of complaint?
Also, as someone who works with the public on a customer service basis, last names aren't always on the name tag. My first name and last initial are on mine for my job. If a first name is all you can get, yet you're specific about the rest of the complaint - trip dates, etc. - why wouldn't that be sufficient?