How can I unlock an iPhone Locked to Owner?

For starters, where did you purchase this iPhone? I believe you are referring to the Activation Lock, which is a security measure designed to prevent others from using your device. This is sometimes used on resell devices to take advantage of others. The only way to unlock your iPhone is to contact the original owner, otherwise it cannot be bypassed and is practically a brick. Try asking for a refund. Next time, only buy from trusted sources, so you don't get scammed.

Please read this informative user tip on the risks of buying resale Apple products ⇢

The All Too Common SAD Reality of Buying … - Apple Community

Apple cannot unlock the phone unless you can provide documented proof that you are the original owner.

The phone is completely useless to you unless the previous owner can provide you with the Apple ID and Password that was used to lock the phone.

If they can't, return the phone for a refund.....if you can actually find the seller now......since they have probably disappeared.

Not unusual to find stolen devices for sale that will be completely useless to the buyer. That will continue as long as they find people who would be willing to buy them. There is nothing Apple can do, so Buyer Beware!