iPhone keypad searches contacts instead of responding to prompts

Calling a business, I was asked to press keys on the keypad as responses. But when I did, a little message appeared suggesting that those keys were being interpreted as a search on contacts, as if to add someone else to the call. The machine on the other end of the line seemed not to hear them. How do I opt out of that behavior, and go back to the tried and true?

Incoming call response is set to FULL SCREEN (already) but this was actually an outgoing call.