This scam gets you just by answering your phone. The alert below is from the Andover Police Facebook page. Upton Daily was alerted to this scam by someone who received a call which originated from Grenada and thought it was strange, did some research, and found the alert below.
PHONE SCAM ALERT:
There is a new phone scam that is occurring and some of our fellow employees have already been targeted. The scam is calling your cell phone, when you answer the caller hangs up immediately, and you are being charged approximately $20. If you call back the number you may be charged $9 a minute. To avoid the scam keep an eye out for mystery calls from these area codes:
(268) Antigua
(809) Dom. Rep
(876) Jamaica
(284) British Virgin Islands
(473) Grenada
***Upon Daily has been notified by readers they believe this alert may not be completely accurate indicating other sources have reported a charge is only incurred when the number is called back. The above alert was taken from Andover Police facebook page and can be found here https://www.facebook.com/andovermasspd 2/4/14 8:00 p.m.***
UPTON DAILY 
According to the news sources I’ve read this is not true (NBC, CBS, etc.). You only get charged if you call the international number back.