Ring, ring. (Silence.) Oops, you missed that call. Maybe you should call back and see if it was important.

Do not fall for this scam, especially if the number is in the 649 area, a U.S. group warns.

If you do, your next phone bill could include a charge for the services of an erotic chat line in the Turks and Caicos, a British outpost in the Caribbean whose area code is 649.

It may seem you just didn't answer in time, but that "missed" call could be a deceptive come-on. (Canadian Press)

The warning is from MyWireless.org, a Washington-based advocacy group with ties to the U.S. telecommunications industry.

"Wireless companies have detected a pattern of calls that ring their customers' number once or twice and then disconnect," the group says in a statement.

"When the number appears on the customer's cellphone as a missed call, it appears to be a typical domestic three-digit phone number starting with the 649 area code."

Customers who return such calls may find themselves connected to an adult entertainment service, it says, "and end up being billed for expensive international call and chat line charges."

The scam is a twist on a well-established tactic of leaving e-mail or answering-machine messages urging people to call what turns out to be an offshore number to collect a prize, the group says.

"MyWireless.org urges wireless consumers to always check an area code first before returning a call to an unknown caller. Be skeptical about area codes you don't recognize, especially: 649 (Turks and Caicos); 809 (Dominican Republic); 284 (British Virgin Islands); 876 (Jamaica); 758 (St. Lucia); or 664 (Montserrat)."

'If you return the call, you may be unwittingly putting money into the pockets of scam artists.'—U.S. Federal Trade Commission

In a fact sheet on phone scams, the U.S. Federal Trade Commission notes that calls to certain offshore locales, many of them in the Caribbean, do not require the international prefix 011, so it may not be obvious you are calling a foreign number.

"In many cases, the return-call number is an international pay-per-call line, with a three-digit exchange that looks like an American or Canadian area code," the federal agency says.

"The message may falsely claim that a family member has been injured, that you’ve won a prize, or that there’s a problem with your credit. If you return the call, you may be unwittingly putting money into the pockets of scam artists."

Rules requiring clear disclosure of the cost of the call do not apply to international pay-per-call services, it says.