My housemate is from New Mexico and tried to call there recently on our landline. And he can't reach his parents because they recently added a new area code in NM (575) which seems to be the same as a local exchange (in Washington State). So when you dial you get as far as 1-575 and the system tells you that it can't complete the call unless you dial 1-509 - but thats in Washington. The nice(?) people at centurytel told him to "unplug all the phones in the house and plug then back in". Right. For more fun (and information) try : his livejournal entry and this followup where they toss out the trouble ticket.