Where did you make your reservations? If you made the reservation through a thirty party like ÖBB, I think your only option might be to ask at a ticket office.

I’m pretty sure that if you buy them from the Trenitalia machines in the stations, you can select your seats at the time. There are usually seats available on the day - even a few minutes before departure.

Thank you for your response. I made a seat reservation on the website https://www.eurail.com/en. Can it be changed if booked through eurail.com?

You won’t be able to change seats with Eurail. You might be able to change them if you ask at a Trenitalia ticket office. If all else fails, just find two seats together and ask the train manager if it’s OK. (Do be aware somebody might be joining the train at a later stop.)

I’m surprised you were placed in different carriages. Did you book both reservations together?

For future trips, you can book with Italiarail. It will let you see the seats they’re about to assign (but not actually change them) which is better than nothing. If you don’t like them, you just run the search again!

See Option 1 here: https://www.seat61.com/interrail-and-eurail-reservations.htm#Italy

(I was wrong about being able to use the machines in stations, but you can buy reservations at the ticket office)

I’ve always used Option 2 - ÖBB. It has no booking fee. You can’t see or select your seats, but any reservation service should try to seat you together unless the train nearly full.

Many Thanks, your information is very helpful,

By the way, can I ask another question? Actually, our itinerary starts from Amsterdam to Interlaken, Interlaken to Milan, and Milan to Rome, all connected to the euro global pass. For the Amsterdam to Interlaken train, the option we chose did not require a reservation, for the Interlaken to Milan, we booked a seat reservation and luckily got the same carriage even though the seats were not close together, while for the journey from Milan to Rome we got a different carriage.

Is there any advice for our journey from Amsterdam to Interlaken? This is our first time using a euro global pass and taking an intercity train. At this moment we are a little worried that if there is no seat reservation, will the train be full and we will not be able to leave at all and have to find a train on a different day and date?

What route will you take from Amsterdam?

Most trains on that route don't require reservations - you just find an empty seat and sit down. But the Eurostar from Amsterdam-Brussels-Cologne needs reservations in the unlikely event you're going that way.

It can be worth getting reservations on the German ICE, even though they're not compulsory. Particularly if you're travelling at a busy time. You can get these on www.bahn.com for a few Euros. You can't reserve the Swiss trains, and you don't need to.

Even if every seat is full, you won't miss the train. You can still board. In this situation, I tend to head for the dining car and hang out there for an hour, then see if any seats have appeared.