I called the UK yesterday because my seat selections seem to go away every so often!
1. They wouldn't help without the Alitalia PNR
2. When I explained that I thought she could find it by name, flight number and date, she had a revelation and located the booking.
3. She didn't understand why there was no longer a seat assigned, but offered me a few crappy examples at the back of the Business cabin
4. I took the best they had left and just sighed.
5. May be time to look for another carrier.