How unlock the Icloud with a different apple ID account

Ask the seller to try the links below to recover their Apple ID/password. They can also contact Apple ID Support. If they refuse, ask for a refund.

Apple ID - How to find your Apple An iCloud e-mail address is an Apple ID.

Apple ID - Find

Enter your Apple (iCloud) ID and click Forgot Password.

Apple ID - Manage

Apple ID – Forgot Password

If necessary, there is a contact link.

Apple ID Support

Apple ID Support (2)

Apple Support by e-mail or chat Select your device, Battery, Power and Charging, then Power adapter not working to get a chat option. If you need to talk to them, ask them if they will do a Skype or FaceTime with you.

Apple Support using Twitter

Unfortunately the only way to unlock a device in activation lock is with proof of purchase of the device, or knowing the apple id and password. Otherwise you have a brick.