iCloud locked
I bought an iPhone 6 from someone online not realizing that it’s locked to the iCloud activation? How do I get in touch with the previous owner to unlock it so I’m able to use the phone I bought for me?
Find My iPhone Activation Lock - This is a security feature, presumably in part to deter re-selling of stolen devices.
http://support.apple.com/HT201365
Turn off Find My iPhone Activation Lock (formerly: Activation Lock: Removing a device from a previous owner’s account) - An activation lock can only be removed using the log-in information for the account that applied the lock.
https://support.apple.com/HT201441
Get the owner of the account to remove the lock or return the device for a refund. It is otherwise useless to you.
If the owner has not provided contact information as a message showing in the login screen, there is no way to contact the owner unless the person who sold the device knows them. Apple will not tell you the original owner, presumably for privacy reasons.