The Federal Communications Commission is warning consumers about a robocall scam that’s been popping up around the country, and recently made its way into East Tennessee.

According to the FCC, the so-called “One Ring” scheme targets specific area codes in bursts, frequently calling residents multiple times in the middle of the night. The commission said scammers are likely trying to get people to call the number back to rack up expensive, per-minute toll charges.

Some of the calls are using the 222 country code of the West African nation of Mauritania, while others used the 232 code from Sierra Leone.

Officials say never to call the number back.

The “One Ring” scam typically involve robocallers that call a number, then hang up after a ring or two, and possibly calling repeatedly. If you call the number back, it could run up a toll that largely gets back to the scammers, according to the FCC.

If you’ve received one of these calls, you can lodge a complaint on the FCC website; and be sure to check your phone bill for any charges you don’t recognize.