No resolution to product that doesn't work

I bought a wifi camera from this place. It will not connect and gives me an error message that the serial number of the device has already been used. This means it is a second hand device already used by someone else. It is IMPOSSIBLE to reconnect it no matter how many times you reset it. Customer service sent me one message back to tell me to connect it to the app as if I'm an idiot and even when I told them in the first message that 2 other exact same cameras I bought from them at the same time have connected successfully. Every response I sent them after that is just being ignored. Four emails in total. I want a refund.