How to unlock a used iPhone linked to iCloud that I don’t know?

If the iPhone has the activation lock on, the old owner will have to cooperate in order for the phone to be of any value to you.

If you cannot access their iCloud account and turn off the 'Find My iPhone' app, you will have a fancy paperweight.

Hi

Only the owner who knows the activation lock can remove it.

You cannot use iPhone.

Cheers

Brian 🇬-1F1E7;