The tricky part here is that one digit can be 3-4 letters, and you don't quite know which one they meant without asking them.
There are two approaches really: ask them to enter '3' 3 times for the letter F, like the old days of texting via T9, and then do all sorts of insane logic in architect to track how many of each digit and where they paused OR have them enter '3' for letters DEF and then ask them which letter they wanted - which is equally dirty.
You could use a voice bot to ask for their name and hope the bot can capture and transcribe the name cleanly enough for the API call.
Or, find another value to search with in the API... with numbers.
------------------------------
Brad Murlin
Zillow, Inc.
------------------------------