This post on Allakhazam says the number for Square Enix support is
(1)-858-790-7529 ? Don't understand american phone numbers so I dunno if that's correct.
http://ffxi.allakhazam.com/forum.html?f ... howmany=50
I can't remember if they're mandatory or not now, but don't forget that the "Square Enix Account" thing is new in the past year or two, and not the same as your old PlayOnline ID (which is what you'd have used 7 years ago, written like ABCD1234).You can sign up for an SE account and then link your PlayOnline ID to the account on their account management site, and then log in with that. I've forgotten whether this is mandatory or if you can just use your old PlayOnline ID. I've definately done this so maybe it's required.
http://account.square-enix.com/
(Services and Options > Link Settings)
EDIT: If you signed up for FF14's beta, then you should already have a Square Enix account, and just need to link your old PlayOnline ID to it.