gradually building a script

So, when I get a spam call, I’ve taken to saying “may I speak to your supervisor, please?” as a variant on “have you heard of the Telephone Preference Service?”, as that was getting boring.  This new question usually leads to them hanging up straight away, but today I got a different response, so I need to extend my script.

ring ring
me: answer phone
me: Hello
either a silent pause, or noisy background before anyone speaks, alerts me to probable spam
them: Hello, am I speaking to XXX? [there are many possible variants of XXX here]
me: may I speak to your supervisor, please?

branch point:
them: [hang up]
OR
them: no you cannot
me: [hang up]

So I need to start scripting from “no you cannot”.  I’m thinking of “why ever not?”, to see what happens next.  Or is there a better response?

It’s more fun playing this as an adventure game (for a while, at least), mapping out a route through to … wherever next?