I don't agree that it is a legit number from the FDA. The male who called our number could barely speak English and sounded Indian. He stumbled all over his words and when I asked where he got this number (as it is unlisted) he said... this is from the government. He was asking for my husband's name, originally, and asked if I was he. (I'm female, obviously)...when I said no, he hung up.
The number may well be used by a real federal office, making it hard for a scammer to resist spoofing. Any "medical compensation" award claim offer coming out of the blue from a South Asian boiler room is going to be premised on a class action lawsuit you've never heard of and maybe doesn't exist. You'll be asked to pay a "processing fee" or similar to collect your prize. None of the above factors into how real class members in America are notified and compensated. It's one of the endless forms of advance fee fraud currently popular.
Other comments here already indicate "Scam Crop Rotation", the work of an illegal call center working multiple fraud scripts.