My complaint:
While booking my train tickets from Rome to Venice (and return), at a specific time slot it was sold out so I had to do it again. The second time around, I was so focused on the time slot, I have NOT changed my destinations. So I bought the tickets (200 euros!). By the time I was downloading the tickets to put it in my mobile wallet I saw a different outbound (Venice-Rome, Rome-Venice instead of Rome-Venice, Venice-Rome). Logically I wanted to exchange (or cancel it to buy a new one), but they immediately said it was not possible. Meanwhile this incident happened on their website.
Suggested solution:
By allowing me to at least exchange the ticket as how I originally booked it.