How can I unlock locked iPhone?

Which One?

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

If your phone is carrier locked - How to unlock your iPhone for use with a different carrier - Apple Support

How to unlock your iPhone for use with a different carrier - Apple Support

If your phone is Activation Locked - How to remove Activation Lock -

How to remove Activation Lock - Apple Support

There are many locks in which you could be referring to on your iPhone that we don’t know, so please clarify. Carrier Lock? SIM Lock? Activation Lock? Passcode Lock? Security Lockout? Something else? Those are to name a few of the common ones.