i'm betting you accidentally pocket dialed the SOS number. This has happened to me twice, because my phone was in my purse and the keypad wasn't locked. I, like a total idiot, accidentally contributed to emergency lines being clogged by stuff banging around in my bag.
This is the San Francisco police dept. I witnessed a hit and run last night and called 911. A few minutes later after I gave a description of the vehicle, a woman called me back from this number with some follow up questions. So it's indeed a real number from the 911 dispatcher.