Many of the local listings seem to be hijacked by a single national company with local looking listings. Their numbers all go to the same dispatching service and it's impossible to find a "real" local locksmith.

And stay away from them. I asked for this service done and they insisted that they had to change all the hardware -- that I was a total idiot for thinking they could just swap out the cores. In the end they handed me a bill for $500 for only two doors. Since I hadn't gotten a proper estimate from them up-front I chalked it up to a life lesson, but they were incredibly nasty to boot.