You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Mark Thomas.

ASSISTANT: Mark Thomas, how may I aid you?

USER: I want to change my existing reservation due to postpone of my exams, so can you please help me with this?

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, no reservation is available by your name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.