If you've recently received calls from West African nations, you are not alone.
The Federal Communications Commission issued a warning to consumers on Friday about scam calls coming from country codes 222 and 232.
The robocalls coming from country codes, identified as Mauritania and Sierra Leone, respectively, ring your phone once and hang up.
Stop. Don't call back!
"Consumers should not call these numbers back," the release said, adding the toll charges are "largely paid to the scammers."
How does the scam work?
Typically, the calls come in late at night and are often repeated several times.
"These calls are likely trying to prompt consumers to call the number back, often resulting in per minute toll charges similar to a 900 number," the FCC explained in a release.
It is called the "One Ring" or "Wangiri" scam, which targets specific area codes in bursts.
Reports of widespread calling have occurred across the country including Arizona, Texas, Oklahoma, Louisiana, Washington, D.C., and New York, among others.
In some reported cases, the scammers allow more than one ring and leave urgent messages asking you to return the call.
What does the FCC suggest?
The FCC recommends never calling back numbers you don't recognize, "especially those appearing to originate overseas."
The agency also suggested asking your phone company to block international numbers if you never make international calls.
And always check your phone bill for unrecognized charges.
If you received a scam call, file a complaint with the agency.
Massive amounts of calls are made easily and cheaply thanks to advances in technology, the FCC said.
Scammers use spoofing tools to hide their identities.
"The FCC is working to combat scam calls with enforcement actions, a strong push for caller ID authentication, and support for call blocking tools," the agency said.