Another giveaway is an extra pause before they start talking. This is call software that lets them dial a bunch of numbers at once until someone answers and it switches the person that answered over to an available headset.
If you answer and say hello and there's an extra second just hang up. They'll call back if it is important.
There’s also a very distinct “bloop” sound from their phone system, I assume it’s the sound of “connecting” you to their conference. Honestly, that is a 100% signal of a scam call that would be trivial to detect en masse in an automated system.
I honestly just literally never answer the phone unless its already in my contacts. If it's so important, they'll leave a message.
If the message mentions anything about stupid stuff like tax fraud/social security number its just immediately deleted, you'd 99% of the time receive official mail for anything about these items.
This is my advice to my parents now, who sometimes get anxious over the disgracefully manipulative bait these scammers deploy.
"If it's an Indian, hang up."
If there's a legitimate need to get in touch, they will find another way. My (naive) hope is that this might also discourage offshoring and/or reward companies employing Americans, if enough people do likewise.
If you answer and say hello and there's an extra second just hang up. They'll call back if it is important.