I read this thread after buying tickets online through Alitalia website and not receiving an option to select seats. Then visiting 'My flights" and seeing that seats were 'unassigned'. I then went to the codeshare airline Bulgaria Air and was able to retrieve my reservation and it too had no seat assignments. After reading through their website I saw that I had to contact Bulgaria Air customer service center and after poking around some more I found an email for them. I then sent a very complete email explaining my seat preferences and included everything from my reservation information like the PRN=alpha booking number and even our ticket numbers and the type of ticket with restrictions (indicating I had a choice of seats as paid for in this ticket price). I did so in text (not as an attachment). Within 12 hours I received a pleasant reply along with seat assignments that now show up on my Alitalia 'My Tickets' page. Hope this helps others.