Hi! It's me again!
Hi! What's up?
Well, since I talked to you about an hour ago, I've found that I won't be able to go bowling with you as we had planned. Something important has just come up.
Oh?
Yes. My boss is insisting that I work this afternoon, and there's nothing I can do about it. I hope you understand.
Of course I do. Let's plan on going bowling some other time.