Overview
There are a couple ways to disable Find My on an Apple device. You can either go to your device's Settings and turn off the Find My feature or you can disable it remotely using iCloud.
Resolution
Turn off Find My on an Apple device
Removing a device from Find My.
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Open the Find My app.
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Locate the device for repair in the list can click on it. 
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Scroll down and click Remove This Device. 
Removing Device from Apple Account
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Open a browser (not on the device to be repaired) and navigate to https://account.apple.com/.
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Sign in to your Apple account.
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Go to Devices. 
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Fin the device to be repaired in the list and click on it. 
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Scroll down in the device window until you see Remove from account. Click it. 