user lock

It appears that either the previous owner did not properly prepare this iPhone to be sold or you are in possession of a lost or stolen phone.

For the former, you will need to contact the original owner so that they can remove Activation Lock from the phone. If you are able to get a hold of them, then provide them with this support article so they can do so.

• What to do before you sell, give away, or trade in your iPhone, iPad, or iPod Touch - Apple Support

If it is the latter (or even the former), you can get with the seller to return the phone to them and get your money back.

Sorry, but no. Activation Lock is Apple's method to prevent access to a lost or stolen device. If you can't get a hold of the seller, then chances are they sold you a stolen phone. As Dogcow-Moof has already stated, it may be time to contact your local law enforcement agency.

No.

If you bought it via a known web site, you may want to contact that site and notify them of the fraud.

Depending upon how you paid for it, those payment methods may also have fraud protection policies.

Finally, you may wish to contact a law enforcement agency.

Which, if he won’t respond to you, makes it fraud unless he specified it was a non-working phone.

Sadly yes, but you can still report it to local law enforcement.