We have booked five "Economy" tickets on the Italo train from Venice to Rome for October. We have a possible issue that may lead us to decide to change to an earlier train. The tickets are changeable with payment of a 20% fee, which is fine as the tickets were cheap. My question is, will we have to pay an additional supplement to "base fare" if there are no Economy tickets left in our travel class when (if) we make the change? I know with airline tickets we would---one pays the existing price at the time of the change. But I cannot find this information on the tickets themselves! or on the website.
There are Economy tickets left right now on the earlier train, but I would have to call to change them, and the last time I called Italo it did not go well (bad connection, long waits, difficulty communicating). So I am wondering if I dare wait until we get to Venice (5 days ahead of our travel,to Rome) and make the change in person.
Thanks for your help.