How to unlock an iPhone from a previous owner?

Sorry, but only the previous owner can disable the Activation Lock, and without a proof of ownership, like the original purchase receipt, Apple can not unlock your iPhone.

How to remove Activation Lock - Apple Support

Additional Support - Activation Lock

If you see a "Locked To Owner" message, one referring to iCloud locked, or activation locked:

Read this article about removing Activation Lock --> How to remove Activation Lock - Apple Support To remove the lock you will need either:

-The account information that set the lock (if the previous owner is deceased, read —> How to request access to a deceased family member’s Apple Account - Apple Support )

OR

-The original sales receipt from Apple itself or an Apple approved vendor. Other ways you may think might be “proof” of ownership or purchase, such as having the box or a receipt from a third party vendor such as Ebay, will likely not be acceptable by Apple. Apple may have no way of verifying the authenticity of other methods. If you have an acceptable receipt, ask Apple to unlock the device —> https://al-support.apple.com/#/additional-support

If it is asking for an account that is not yours, take it back to the person from whom you received it. Get them to do the things in this support article or ask for a refund --> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support There is no way to discover the owner of a device unless they left a message to display on the device when it is turned on, or the person who gave you the device knows them. Note that the device cannot have Lost Mode set on it. If your device has been taken over as a result of you having entered a scammer’s Account then the scammer may have set Lost Mode too and the device is lost to you.

Return or recycle the device if you cannot unlock it; it is useless to you. From the very bottom of Apple Trade In - Apple :

"Does Apple offer recycling?

Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."

When considering future purchases, browse this: The All Too Common SAD Reality of Buying … - Apple Community