OK, then, the IMPLIED question inside of "I hate to bother her for one letter."
Since "letter" in this context doesn't make sense if it's the same letter as the confirmation letter, it must mean letter as in letter of the alphabet. So I got that the deeper issue is if they will not let them check in, because they are down as Smith if they are actually Smyth, for example.
To me, that's a bigger issue than who can and cannot contact MS. IF it's worth bothering the owner, for a difference of one letter.