How I allow call-back on my iPhone 12 Max?

The only thing I can think of is after you hang up the call, while in the Phone App, go to Recents on the bottom of the app. Tap that, then tap the number you originally dialed and you'll call back the number you dialed, without having to enter the numbers again.

Do you mean from an automated phone system where it may suggest to tap a specific number if you want to be called back?

If that is what you are asking when you are on a call, see the green icon in the upper left corner of your screen. Tap it. This brings up options including number pad, speaker options, etc. Tap the number pad and choose whichever number they suggest to get a call back.

If this is not what you are asking, please provide more details.

That's correct. If you are still inside the Phone app and you see the keypad or speaker options, there be NO green icon in upper left corner. You will see the green icon if you on a phone call and you move out of the Phone app to another app or your home screen. If you do that, you'll see the green icon in the top left corner, to let you quickly return to the Phone app options.

There is no button for Call Back on iPhone. I don't know what your unemployment office is expecting you to do to get a call back, but there isn't a button on the phone you tap for that. There has to be an option in their system to prompt you to enter a number to get a call back.

I'm sorry, I'm not familiar with a "call back" feature on iPhone. I've never been instructed to use a calling back feature.

I'm thinking there must be something additional the unemployment office instructs on their end to initiate a call back?

What was on your screen then? Did you see the Keypad button and speaker options? If you did, there wouldn't be a green icon in the upper left hand corner of the phone, because you were still in the phone app.