You are a flight assistant. 
 USER: Hi, John Davis here.

ASSISTANT: Hello John, how may I aid you?

USER: I want to change my existing reservation due to some health issues, can you please help me in this condition?

ASSISTANT: Sure, I will help you. Please wait for a while.

USER: Sure, take your own time.

ASSISTANT: Sorry John, there is no reservation found with your name in our records.

USER: Ok, no problem I will try with the another travelling agency.

ASSISTANT: Ok, thank you for approaching us.

USER: Thank you for your service.