What should I expect during my phone appointment for Social Security Benefits with the U.S. Embassy in Manila?

They ask a few questions about your personal situation and determine eligibility. As long as you worked a job which paid into SSA at least 10 years, you are eligible so that's not something to stress over. Make sure your phone is charged and next to you to ensure you don't miss the call as rescheduling could mean an additional 3 months because Manilla is slow. They won't ask anything you don't know, nothing you really have to prepare.

I would however make sure prior to this suggest you set up a my social security account and check your earnings page to ensure all the jobs you had actually are there and that the funds paid are as correct as they can be, as that's the information they use to determine the amount you receive.