I bought a seat reservation for the night train from Roma to Torino tonight. I saw there are still couchette beds available for reservation, and would love to make an upgrade. I just don’t know how to do it. 
Can I go to the station and ask for an upgrade to a couchette bed? Would it be possible to upgrade inside the train?

There’s a strike affecting public transit in Rome today, so I doubt I’ll make it to the main station.

Has anyone had any experience with this?

Thanks in advance.