When you move, a whole bunch of information about your move and the fact that you moved becomes available to local business owners. I'm not sure what process is in place that does this (maybe a mailing-address change card you give your post office?) but it is what happens, in the US at least. Usually you'll get a coupon book for local businesses- the fact that they know you just moved in is due to the same process. Anyway, ostensibly bad actors would likely easily get in on this, and frankly it's a clever move because they know you're frazzled and in a state of being disarmed and they knowing you just moved (and where, which explains knowing the name of your electric company) gives them an air of legitimacy and that's the perfect time to strike. Also $350 is not an entirely unreasonable amount of money to ask for.