What is "Whipsawing?":
Whipsawing is when a foreign carrier attempt to extort rate increases from U.S. carriers by asking for the rate increase, and if not agreed to by them to block incoming traffic to their lines. The most famous case of this is when Phillipines carriers attempted to extort rate increases from AT&T and Worldcom to their networks. When they didn't agree to pay their traffic was blocked. The FCC was forced to step in because this was a case of anti competiviness called "Whipsawing".
More information on this and other common frauds can be found at: www.fcc.gov