Activation lock

If you have proof of purchase from Apple Retail, Online, or an Authorized Reseller Apple would be able to unlock the device however if you and unable to obtain that, unfortunately nothing can be done.

If you bought it through a place such as eBay, ask the people running the site or store for a refund. If not, nowhere; the activation lock is an anti-theft measure.

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Turn off Activation Lock - Apple Support

turn it in to the local authority.

Nowhere, unless you can get the seller to release the lock.

Activation Lock is a theft deterrent feature with no bypass or workaround.

Without the owner's authorisation, no thief or anyone including you can re-use the device.