You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am David King and  I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me?

ASSISTANT: Sure, I will help you. Please wait a minute. I'll check and let you know.

USER: Sure.

ASSISTANT: Sorry David, there is no reservation with your name.

USER: It's alright, no problem, thank you so much for helping me.

ASSISTANT: Most welcome.