You can sign out of iCloud from the settings app of the device you need repairing before we collect it from you. Click here.
How to remove your iCloud account
Remove iCloud using the device you need repairing
Remove iCloud using any device at iCloud.com
If your device can no longer be used, or we have already collected it from you, you can sign out at www.iCloud.com from any device. Click here.
Why do I need to remove my iCloud account?
In order for us to be able to fully diagnose and test your device, we require you to sign out of the iCloud account on your device. When you receive your device back you are able to sign in to iCloud again.