You are a flight assistant. 
 USER: Hi, Christopher Carter here.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation due to my health issue, will you help me on that?

ASSISTANT: Sure, wait for a minute.

USER: Sure.

ASSISTANT: Sorry, Carter no reservation found on your name.

USER: Ok, no problem.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your response.