We took the Zürich to Amsterdam connection on Thursday evening and were told that the couchette wagon that we had booked was not available once we were on the platform. It was replaced by an SBB first class coach. Those are usually nice but not for an 11 hour ride. Furthermore, the lights don't dim that much so it was hard to sleep. My pregnant wife resorted to sleep on the floor. The breakfast that comes with a couchette booking was also missing. We were not offered any compensation and were told to write to OeBB.

Write them and list all that wasn't as advertised. It takes a long time for a reply and you will probably only get a coupon but the more people complain the more likely they will stop these shenanigans.

This is what I did and they gave me a coupon for at least part of what I paid but I have no use for it as I almost never travel to Austria.