I get people all the time who walk into my store talking on their cell phone. They continue to talk the whole time they are in the store, until they reach the cash register.
I then tell them I'd be glad to help as soon as they are done with their call.

I just recently got a cell phone at the insistence of the lovely Rhona, but it just sits on a shelf in my office. If your call is that imporant, leave me a message, or call me back on my land line.