Activation lock

You need to enter the last Apple ID and password that were used on this iPhone.

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Turn off Activation Lock - Apple Support

1. If you can’t remember your Apple ID email, look it up here
2. If you can’t remember your Apple ID password, reset it here
3. If you can’t remember your security questions to reset your Apple ID password, call 800-APL-CARE (800-275-2273) to see if there are any other options to recover your account
4. If all of the above fail, visit an Apple Store with proof of purchase where they can usually remove the Activation Lock, but the device will be erased in the process

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you.