This is the 3rd set of unknown calls from today, 5-9-2012. I received two calls from this number today, after having received four calls from 577-824-7842 & two from 622-778-2478. Each time I answer the caller hangs up. These area codes apparently do not exist or, at least, not in the U.S. This is really irritating, but I do not know if there is anything that can be done.