What SU number did you call? The Moscow ones seem to be answered more regularly than the US ones. There is an email address below you can send questions like this to. I assume they'll handle seat requests though I, even as a SU Bonus Gold member, have never gotten advanced seat confirmation other than when booking online and choosing seats then. Sometimes those don't even hold till you actually check in. Did you book at www.aeroflot.ru or some other site? The Aeroflot site gives you the chance to choose seats before finishing the transaction. Not sure if others do or not.

The email address you might try contacting is:

[email protected]

Good luck and report back what you are able to accomplish.