WASHINGTON (CBS NEWS) – If an unknown number with a “222” area code rings up your phone in the middle of the night – don’t call back. The FCC is warning of a new “One Ring” or “Wangiri” robocall scam that tries to get people to call back that number, resulting in toll charges.

The agency says the country code originates in Mauritania, a country in West Africa. There have been widespread overnight calls reported in several states.

“Generally, the One Ring scam takes place when a robocaller calls a number and hangs up after a ring or two,” the FCC says in a recent consumer advisory. “They may call repeatedly, hoping the consumer calls back and runs up a toll that is largely paid to the scammer.”

The FCC is urging consumers not to call back any numbers they don’t recognize, especially ones like these that appear to come from overseas. People should also monitor their phone bill for unusual charges.

Anyone who receives a “One Ring” call can report it to the FCC here.