Dialogflow ES dynamic entity or training phrase

I'm using Cisco CVP IVR to integrate with DialogflowES and Google cloud Speech to text. My IVR collected the caller's account number and retrieved the associated caller's name from a database. Now I want the caller to tell me their name and I want to see if it matches that from the database.

Since there are millions of crazy names/spellings, using an Entity Type of @sys.person or @sys.any isn't very useful.

So, I want to pass the name to Google almost like a 'dynamic grammar' (perhaps along with a few other decoy names), and have Google try to match what the caller says to one of these entries.

Is that possible to pass Google Dialogflow ES agent a list of names (I guess in a payload) and have that be used to build (or expand on) an Entity dynamically during the call?

I haven't used API.AI but is it possible to use fulfillment to create something like this dynamically at runtime based on what's passed in from my IVR? This sample is based on Dialogflow Training Phrases through Dialogflow REST API:

"trainingPhrases": [
   {
     "name":"",
     "type": "EXAMPLE",
     "parts": [
       {
         "text": "<<use a name1 passed from the IVR during the call>>"
       },
     ]
   }
 ]

I've tried modifying fulfillment, and I can at least access what the caller said and what the payload passed in was (the actual person's name). But I don't know how to limit what the agent is listening for to be a small list of names passed in.