As we all know, robocalls and vishing (voice phishing over the phone) have become an increasing annoyance in our everyday lives.  Whether the calls are on our home phones, cell phones, or office phones, we've all been bombarded with calls that were phishing for personal information, alerting you of financial issues, threatening arrests if you don't send money, or just plain trying to sell you something that you didn't ask for.  Many times it's easy to figure out what's going on and to just hang up.  But occasionally, it may not be that clear.  Many people have been victimized by these scams.  To help you determine whether you are being scammed or not, here are some tips:

• Think before you speak. Scammers want you to act — and give out information — before you think things through. The person on the end of the line may sound sincere and trustworthy, but that doesn’t mean they’re legitimate.
• Have your guard up with automated calls. Be particularly skeptical of scare tactics, prizes, and special offers.
• Be aware that caller ID can be easily spoofed by scammers.  
• Verify phone numbers before calling back. If you’re given a toll-free number to call, look up the correct number yourself, either online or using the back of your credit card, for example.
• Use a different phone to call back. Attackers have ways to keep the line open even if you hang up and try to call your bank’s correct number. You think you’ve reached the bank, but you’re still connected to the scammer.
• Perform an Internet search for the phone number of the caller or the one that they give you over the phone.  There are many websites that track whether individual phone numbers are suspicious.
• Note that organizations such as the IRS will never make first contact with you over the phone.
• If a bank is supposedly contacting you, hang up and call the number listed on your card or their website.

This articles gives additional insight to the problem: 

https://www.wombatsecurity.com/blog/vishing-attacks-whos-really-on-the-line