If you have proof of purchase, as explained in this article, contact the official Apple Support, and ask them to disable the Activation Lock.
Contact Apple Support - Apple Support
There are a few requirements before your contact them:
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You must be the owner of the device.
Apple may require proof of purchase. Proof of ownership must include the product serial number, IMEI or MEID.
Your data on the device will be erased.
If Apple unlocks Activation Lock on your device, all files and data stored on your device will be permanently erased. Please note, restoring your device from a local backup will re-enable Activation Lock.
We can’t unlock a managed device.
If your device is owned by a business or educational institution, please contact your IT department or manager. We also do not accept bulk requests.
Your device must not be in Lost Mode.
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copied from: Additional Support - Activation Lock