The requests need to go through MS (the online room requests offered when doing online check-in are too limited these days). You can call and possibly have to wait forever these days for someone to actually answer, if MS answers at all.
An alternative is to send an email using the email feature on the website. Make sure you describe both reservations, including reservation numbers, in the email and make your requests in the email. Note, I personally would probably not request top floor but instead ask for "higher" floor, or, at Poly, 2d or 3d floor in Moorea. Not limiting your self to one floor increases the chances of actually getting an upper floor. MS usually responds to the email within a few days noting your request has been made.
Another option would be to use the online Chat feature but that, like the phone, has often not been working at many times lately.