Hi Bluezulu42,
It sounds like you're wondering how to use the Keypad when on a call. We're glad you've joined us in Apple Support Communities. Let's see if this helps.
If you have another app open, follow step two in "Use another app while on a call" in While on a call on iPhone to return to the Phone App call screen > then press the "keypad" > enter the number(s.) If you're already on the call screen, press the "keypad" button and enter the number(s.) You can see which button we're referring to by opening the link and looking at the illustration there. You'll see the "keypad" button in the top row in the middle.
If you only see the white dial pad in the Phone App, you may be using another app to place a phone call instead of the built-in app that comes preinstalled on your phone.
If the issue remains after following those steps, let us know if you don't see that button, what you see instead.
We hope that helps with your question and take care!