* This is Tony. I'm Mr. Smith's son.

Question

How do you pronounce 'Smith's son'?
It's difficult to pronounce.

* Hold on a second.
Q1) Is 'for' omitted before 'a second'?
Q2) What is the opposite of 'hold on' in the telephone conversation?
Q3) Can we use 'hang on' instead of 'hold on'? Are both the same?

Answer 1

To pronounce, just ignore the "'s" as if it were written "Smith son."

Q1 depends upon what the rest of the context is. "Hold on for a second?"
Q2 If you don't want someone to "hold on" do you mean "hang up?"
Q3 Either "hang on" which seems slangier than "hold on" or "hold on" but essentially they are the same.