You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I be at your service today?

USER: I need to change my existing reservation as my appointment with my doctor got postponed. Can you help me with it?

ASSISTANT: Sure, we are here to help you. Could you please provide your name to check your reservation status?

USER: My name is Thomas Johnson.

ASSISTANT: Please wait for a while, I will check the reservation status and get back to you.

USER: Sure.

ASSISTANT: Sorry we couldn't find any reservation against your name.

USER: It's ok, thank you for the response.

ASSISTANT: Thank you for choosing us.