I'm hearing about similar occurrences. I think it may be scammers trying to "establish" themselves on phone networks by making calls that aren't scams (for a while), then later performing scam calls.
Or maybe they're recording your voice for later impersonation.
Or maybe they are judging your reaction to what they say, to size you up for a future scam.
Probably something entirely different, but still a scam. Scams are just out of control right now, and getting way way worse.