Scam.
It doesn't matter if you rarely use that phone/number. Scammers have the ability to call thousands of numbers a day and they'll keep doing so until they get a live person. You just got randomly selected.
Bad thing is, now they have your name and know you are a "live" number, and naive enough to possibly talk into scamming since you started to fall for it by picking up the phone in the first place.* This is likely to result in an increase in similar scam calling as they will keep trying and also sell your number on "good number" lists they use to other scammers.
Never call back any number. Doesn't matter if it says it's from a government agency, your bank, credit card or your grandson who was just arrested in Mexico. NEVER ANSWER, NEVER CALL BACK. They can say they're whomever they want, and the # on your caller id is meaningless now that spoofing is so easy. They can even make it look like your number is doing the calling!
If you are nervous about it being legit, then look up the agency website or look on the back of your credit card for the direct number, contact them that way to ask.
*I'm not trying to be insulting; you're likely a very good and honest person and those are the types that scammers LOVE because they know that most folks like that don't believe that there are bottom feeding scum out there that will sink to epic levels to scam someone. It is a sad state of the world where you really just can't trust ANYONE any more and being a kind, trusting or decent human being gets you a target on your back now. :(