You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I assist you?

USER: I am Jacob Smith due to postpone of my friend bachelor party, I want to  change my existing reservation.

ASSISTANT: Sure. Can you please wait for a while?

USER: Yes.

ASSISTANT: Thanks for the waiting. Unfortunately, we did not found any reservation matched to your details.

USER: Thank you for your help.

ASSISTANT: Thanks for contacting us.