Hi Mary,
I myself have had difficulty in the past in obtaining our US reservation number from a travel agent here in the UK. In reality, this is a very common request which you should have no difficulties with at all and I would definitely recommend that you call them again to request it. If you are getting nowhere, ask to speak to someone more senior.
You don't actually need your US reservation number in order to make dining reservations and if you arrive at Walt Disney World on 15 October 2012, you will be able to start making your dining reservations on 18 April 2012.
If you are not able to obtain your US reservation number, you will only be able to make your dining reservations one day at a time rather than being able to make dining reservations for the first ten days of your trip at 180 days out.
You can make dining reservations on the Walt Disney World website by clicking on "WHERE TO EAT" followed by "
Make Dining Reservations"
Wishing you a magical holiday filled with memories which will last a lifetime!