My legal first name and last name are the same in English. Norwegian airline didn't let me book tickets on their site years ago. When I called their customer service, the solution they provided was to put my first name as "Mr [first name]"... and it worked!

By the way, you seem to be shadow banned, though it is not clear why. This is your first post since your account creation almost 4 years ago, so it's not like you have any history of writing bad posts. I vouched for you to undead your comment.