I concur,... This is just the SS Office looking to confirm info that was used on your application.
They DID now that I had a question about my Income... They are the SS Office.
Not a Scam.
Yes it was the SSA - the voicemail they left had information that only the SSA could know - that I recently applied for Medicare - they left a toll free phone number for the callback and that was indeed an SSA number, so I felt OK giving the information they required. I had to put "unknown" for call type because you don't have "routine" or "legitimate" in the list of call types