MINNEAPOLIS (WCCO) — If you receive a call from area codes belonging to places like Grenada or Antigua and the phone only rings once, the Better Business Bureau warns not to call back.

According to the BBB of Minnesota and North Dakota, the calls are part of a scheme being perpetrated by scammers who anticipate victims’ curiosity getting the better of them.

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The scheme works only if victims call the numbers back, at which point they’re usually connected with international adult entertainment or chat lines, and are then on the hook for extensive phone charges.

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“This scheme definitely plays on our natural curiosity,” BBB president and CEO Dana Badgerow said. “This scam, like a lot of scams of this nature, will likely die down fairly quickly before popping up again in another form.”

In addition to Grenada (473) and Antigua (268), other area codes that have been reportedly popping up on local cell phones include the Dominican Republic (809), Jamaica (876), and the British Virgin Islands (284).

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The BBB suggests people keep a close eye on their cellphone statements and contact their carrier if they notice any strange or unauthorized charges.