Plz help me I buy a iPhone 4s second hand when I reset it they ask a old apple I'd activation lock ,icant find old owner plz help me.....😢😢😢

iCloud: Activation Lock - http://support.apple.com/kb/HT201365 - This is a security feature, in part to deter re-selling of stolen devices.

Turn off Find My iPhone Activation Lock (formerly: Activation Lock: Removing a device from a previous owner’s account) - https://support.apple.com/HT201441 - If an activation lock was put on a device, only the owner of the account that applied the lock can remove it.

Get them to remove it or return the device for a refund.