I've been getting a lot of these types of calls lately. I guess they all graduated from Phone Scam College at the same time.
This one went to voicemail because I refuse to answer. Usually they hang up after one to three rings. Voicemail registered but no message. I blocked the number but they'll just call back on a different number.
I've also been getting a lot of calls that register as "Unknown" on the caller ID. Can't do anything about those.