Android PIN, locked bootloader

[cash 17]

Hello,

I finally received my phone (albiet with a dead battery that required dissasembly), but I guess it is used, as Android has a PIN. I have tried all of the common PINs and no luck.

I have tried to boot into bootloader using power + vol down. I however get a broken robot icon with the text "No command"

I have tried recover mode using power + vol up, but this just boots into Android.

If I connect to my PC and use the command "adb devices" I get this response:

List of devices attached
778c00e6        unauthorized

 

The bootloader also seems to be locked, so I'm not sure what else to do.

Thanks