Yeah, working in the cell phone industry as I do, I get a lot of calls where I have to explain number spoofing (faking the caller metadata), but that's still weird as hell. Normal spoofing scams are either (1) trying to get sensitive information out of you by pretending to be the IRS or whomever else, or (2) trying to determine if you're a real person by getting you to pick up the phone, on which they will sell your number to other telemarketers. But this is obviously not the first one, and the second one doesn't usually leave voicemails.

(People have the oddest questions about spoofing, honestly. Every so often I have to reassure someone that their phone has not been hacked and is not making the calls without their permission, and that the calls will not appear on their phone bill. Which is not a fear that would have occurred to me.)