You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Catherine Mitchell.

ASSISTANT: How can I help you?

USER: I want to change my existing reservation because my exam was postponed, can you please help me with that?

ASSISTANT: Please wait a moment. Let me check.

USER: Ok, take your time.

ASSISTANT: Sorry, there is no reservation found with your name.

USER: That's ok. Thank you for checking.

ASSISTANT: Thank you for reaching us.

USER: Welcome.