You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you today?

USER: I am Brenda Thompson here, I would like to change my existing reservation, can you please help me in this?

ASSISTANT: I will help you with that.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Sure, take your time.

ASSISTANT: I am sorry to say that there is no reservation found.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Thank you for your service.