Activation code help

If this is a used device, you will need to contact the previous owner to have them log out of iCloud or go to iCloud.com/Find My Phone and erase the device, then remove it from their account. If you can’t do that, the device is useless. 

Activation Lock - Turn off Find My iPhone 

If you are the original owner, take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store.

Genius Bar Reservation US

or contact Apple ID Support. They will need to see the original purchase receipt/paperwork also.

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. 

Apple Support using Twitter

Or fill out and submit this form.

Has your friend gone to the store where they bought it to see if they can get a replacement receipt? If you can't get a proof of purchase receipt, Apple won't unlock the phone. It will be worthless.