You have to wonder who it is that falls for these things.
I do not answer calls that are not in my contacts and I do not respond to voicemails of this type for the following reason: I login to the various accounts I have, from telecomm to financial, on a regular, consistent basis. If I've been 'hacked' I would know it before any fake phone calls.
My mobile carrier account and my bank account alone see one to three logins (by me) a day.
I also have TFA and my passwords would be easy to guess only if you truly know me
Gotta stay safe.
