Take it back to to his place of work and get them to do the things in this support article --> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
Apple used to do it at stores but I don't know if they still do since they have introduced an online service. I suspect if you go to them they will tell you to do it online.
It also depends upon the kind of locking you are encountering. Unfortunately your description means that several different kinds may apply.
If you see a waiting period you can try again after the timer ends. If you wish to proceed with resetting, or if it is disabled/security lockout/unavailable, refer to this support article for various methods that you can use to resolve this. --> If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support Which one you can use depends upon your equipment configuration. If you can use the iOS15.2+ method you may not need a computer.
How to reset your device if you are running iOS 15.2 or later:
Advance step: If you're using an eSIM, contact your carrier before trying these steps and ask for a QR code to set up your eSIM again.
1. From your device's Lock Screen, try to enter your passcode five times until the "[Device] Unavailable" screen appears and your device asks you to try again later.
2. When you're able to, continue to enter your passcode until the "Security Lockout" screen appears and you get the Erase [Device] option in the bottom corner of the screen.
3. Tap Erase [Device], then tap Erase [Device] again to confirm.
4. Enter your Apple ID password to sign out of your Apple ID on your device.
5. Tap Erase [Device] to permanently delete all of your data and settings.
6. When your device restarts, follow the onscreen instructions to set up your device again, restore your data and settings from a backup, and set a new passcode.
You can only reach the "Security Lockout" screen if you have an active cellular or Wi-Fi connection and previously enabled Find My ( Find My - Official Apple Support ) on your device. After you try to enter your password ten times, your device will either erase itself or show Security Lockout and the option to Erase [Device] without a timer, depending on how you previously set up your device.
If you can't follow the above steps (e.g., you are using an older iOS version), you can use a computer to reset your device, as described in this article --> If you forgot your iPhone passcode - Apple Support .
Read the support article for full information. You can also watch the 5 min. 16 sec. Apple video "How to restore your iPhone if you forgot your passcode" at https://www.youtube.com/watch/7s8-zLG9ySQ
Whichever method you use will result in erasing the iPhone. You can, however, restore it from a backup as described in this support article --> Restore your iPhone, iPad, or iPod touch from a backup - Apple Support Some items will restore automatically once you make sure you are signed into iCloud (if you were using iCloud to sync these services).
Here are resources if you are prompted for your username and password and have forgotten them:
If you forgot your Apple ID email address or phone number - Apple Support Note that typically this is an email address you use.
If you forgot your Apple ID password - Apple Support
If you do not have a computer, use the link Find Locations to find an Apple service location, or ask a friend if you can use theirs. This could be either a Mac, or a PC with iTunes. If your computer doesn't recognize your iPhone, iPad, or iPod, read this support article --> If your computer doesn't recognize your iPhone or iPad - Apple Support
Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Do this online at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not detail what currently constitutes proof. Prior to this new online service Apple typically required the original receipt issued by Apple or an Apple Authorized Reseller and documented provenance (so typically it would be the original owner who does this, or a descendant with legal proof of ownership). This will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.
Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support
Finally, if this was a work device it may be it is managed by the IT department at his place of work and Apple cannot removed that lock unless he has the original purchase receipt.