I have never had any problem before arranging anything associated with my stays with Aman's 24 hour reservations and concierge staff based in Sri Lanka.

You certainly can email the executive directors and managing directors at Amanresorts who are all very kind, and the property GMs but I tend to not waste their time on simple booking requests and rate inquiries.

TA's are to a degree helpful booking an Aman... With the properties so small, the chances of upgrades diminish.

Edit: I am certainly not saying it doesn't happen, but you roll the dice. It's very easy to get upgraded in a hotel with 100+ rooms.. I tend to book the suite I want stay in...