iPhone keypad does not work during calls, e.g. for telephone banking

This solution was provided previously but does not work on my iPhone 16 Pro Max.

Some telephone banking and other automated systems, such as for two-factor identification, call you and may ask you to press a key, e.g., star. When you open the iPhone app and select the keypad at the bottom. You press the key, nothing happens. The automated call system continues; it may ask you to press a key again.

By default, the iPhone does not send the keypress. To fix it, do this:

1. Open Settings.
2. Select Phone.
3. Select Incoming Calls.
4. Change the option from Banner to Full Screen. (My iPhone is already set to Full Screen)

Done.