Phone scammers are getting trickier than ever to avoid, a new column on Inc. reveals. Once unsuspecting people pick up, thieves can make money off premium charges, or even use their voice to authorize other bills. However, a quick glance could reveal whether the call means real business or not.

According to Joseph Steinberg, CEO of SecureMySocial, certain area codes can tip off potential victims that something is amiss. In the past, criminals used to hide behind "900 numbers" that racked up high charges, but the public quickly caught on.

Then scammers tried a new approach. Many schemes soon featured the numbers 809, an international area code from the Caribbean that appeared to originate in the United States. As familiarity with that ruse also increased, crooks have since moved on to other islands that still fall under the +1 country code. "Criminals have been known to use caller IDs with the area code 473, which appears to be domestic, but is actually the area code for the island of Grenada," he wrote.

According to AARP, taking calls from any of those foreign countries can cost $5 a minute or more. The bot or person behind it can also persuade listeners to spend money on sketchy timeshares or cruises. In other schemes, people pretend they need help or money because they're in danger.

Steinberg advises never returning a missed call from an unknown number — if it's for real, the person can send a text or leave a voicemail. "Remember that it's unlikely that someone you do not know — who is in distress at a location with which you are not familiar — would dial a random number in another country and ask you to help them," he says. "They would call the police."

To protect your wallet, watch out for 473, 809 and 900 numbers. It also doesn't hurt to check missed calls against the international area codes that start with +1:

International Area Codes With a +1 Country Code

242 — Bahamas

246 — Barbados

268 — Antigua

284 — British Virgin Islands

345 — Cayman Islands

441 — Bermuda

473 — Grenada, Carriacou and Petite Martinique

649 — Turks and Caicos

664 — Montserrat

721 — Sint Maarten

758 — St. Lucia

767 — Dominica

784 — St. Vincent and Grenadines

809, 829 and 849 — Dominican Republic

868 — Trinidad and Tobago

869 — St. Kitts and Nevis

876 — Jamaica

[h/t 10TV