I can't believe this is back...
When I was part of AT&T, I and a few others put together a newsletter that contained information on the international direct-dialed call scam.
The Dominican Republic was always a problem with this, as well as Vanuatu, Moldova, and a couple other destinations that slip my mind. This was big in the day of telephone line modems - often a virus would place phone calls in the middle of the night..
Why - The short version:
A foreign company, and the government of the international destination setup a revenue sharing scam for calls that come in from certain other countries. Since the USA is 'super wealthy' - we are targeted as a source of easy money.
The policy was AT&T would adjust this type of call ONCE and only ONCE, as the international destination would get paid for the call, regardless. But since I haven't been there in 11 years, policies may have changed (and since its been 11 years, my nondisclosure agreement has expired, allowing me to mention this)