There are at least four things referred to as unlocking...
...Activation Lock. You’ll beed the password of the Apple ID holding that lock, or proof of original purchase and matching ID and a discussion with Apple. Activation Lock is a theft deterrent, and it wouldn’t be a deterrent if it were easy to bypass.
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
...Passcode Lock. Reset your device to release thar, if the passcode has been forgotten.
If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support
...Carrier (SIM) Lock. Only your cellular carrier can release that. Contact your carrier.
How to unlock your iPhone for use with a different carrier - Apple Support
...Screen Time passcode:
If you forgot your Screen Time passcode - Apple Support
If this is a used iPhone recently acquired as is probably the most common of these questions, contact the seller and have them release the Activation Lock or refund your money. As has happened to too many folks, the seller will be unavailable, and you’ll have an expensive brick. Contact the local police, or recycle the device.
The All Too Common SAD Reality of Buying a used iPas/iPhone - Apple Community
