You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I be of your helping hand?

USER: I want to change my existing reservation, due to my convocation dates has been changed.

ASSISTANT: Ok.

USER: Can you help me in changing reservation?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: May I know your good name?

USER: Sure, I am Michael Clark.

ASSISTANT: Ok, Wait for a while, I will check and revert to you.

USER: Sure, take your time.

ASSISTANT: Thank you for your time.

USER: Ok.

ASSISTANT: I regret to notify you that, there is no reservation found with your name.

USER: Ok, not an issue.

ASSISTANT: Thank you for reaching us.

USER: Thank you for quick response.