To unlock your iPhone, follow the steps described in the Apple article: If you see an iPhone or iPad unavailable message or Security Lockout screen
If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support
See also -> Help a friend or family member as their account recovery contact
Help a friend or family member as their account recovery contact - Apple Support (IN)
- ask a trusted friend or family member to help you.
An account recovery contact can help make sure that you always have access to your account, even if you forgot your Apple ID password or device passcode.