Just log into member services, use the contact form and put your travel plan number in the subject line. What I love about it is then you get an email confirming that they got your request back (along with the disclaimers) but still, you can save it if need be. After I read what you were told I actually called Aulani (mostly as I had a few other questions) and was able to speak to the front desk who pulled up my ressie and saw the request right there

The problem with a phone request is most often MS will generalize it versus keeping any specifics you want. So for example at OKW last summer they'd have entered "millers road area" when what I wanted was upper floor, water view buildings xx, xx ,xx,xx,xx preferred in that order. And while there aren't any garuntees, I did get my exact request on that one, as well as at Vero so I do think the very specific request can't hurt. A specific villa? Chances are slim but if you give them enough to work with and a clear idea of what is important to you, it should help.
For Aulani my request reads as follows for our ocean view studio.
I would like to make the following room request. 1st choice: Ewa Building, long wing facing the pool, high floor (prefer 12 or higher). 2nd choice: Waianae Building, facing the pool, high floor (12 or higher).
Will I get it, who knows but it never hurts to ask! We will find out in May.