Unless you are the original purchaser DJI will NOT unbind a drone NO exceptions. Unless you can prove you purchased it from them and then only a slight MAYBE. If you lost your drone you don't need to unbind it from the controller. If you found the drone it is a paperweight to you and it will never fly again: UNLESS you post the serial number to a lost and found or DJI. Maybe the Owner who lost it can get it back.
I recently purchased a DJI drone in an auction only to find out many of the accessories were not in the box, most needed was the charger as the Air 2s cannot do USB-C charging in the aircraft. I purchased a new DJI charger and new props and started the drone up only to learn it was already bound to another account. Sigh…
I contacted DJI Support by phone and the next level support at DJI sent me an email, essentially how to unbind the aircraft, asking me to contact the previous owner and have them do it. The auction had purchased a truckload of Amazon returns and had no way of tracking down the owner.
I replied to DJI with that information. They asked for the paid invoice from the auction, which I had and provided. DJI then asked for a letter from the auction house confirming they were the previous owner to the sale and had no objection to unbinding. I wrote the letter with the specific wording DJI wanted and the auction house put it on their letterhead and signed it.
Within 24 hours of sending that back to DJI Support, the aircraft was unbound and I bound to my DJI account.