I need some help with accessing a second hand Galaxy Note 5 I purchased a few days ago please!!!

[AC Question]

I recently purchased a Galaxy Note 5 off of Facebook. The gentleman claimed it was unlocked to any carrier (Canada). Prior to paying, I used an IMEI checker to ensure it wasn't stolen, as well as inquiring with the local carriers that they would honor the phone. Everything seemed to check out. The gentleman had also just done a factory reset on the phone to clear all of his accumulated data. When I arrived home and put my own sim card into the phone, the first screen came up asking for a SIM network unlock PIN. I dismissed this, and tried to the device through other means. I made it as far as it requiring a google account that has previously been synced with the device. Just for giggles I tried my own gmail account, to no avail. I've been trying to get a hold of the guy who sold me the phone for three days now, but of course he's no where to be found. I'm so very upset, hundreds of dollars just gone to waste. It's a beautiful phone, was supposed to be a birthday gift for my daughter. Can anyone please help me? I would be so grateful for any advice (other than to stop buying expensive electronics from strangers.. lesson learned haha).