I’ve found it can be helpful to shift your own attention after someone answers you, but not to a phone (which just makes you look like you’re communicating with someone else).

Look at a flyer on the wall, or your beverage if you’re in a bar, and they’ll follow up if they want to talk and appreciate the reduced pressure either way.

And yeah, never open a conversation with something like “can I ask you a question?” which is usually a trick of a salesperson or beggar to make you acknowledge them and start saying yes.