You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. What can I do for you today?

USER: Due to some issues, I am willing to change my existing reservation. Can you please help me for this?

ASSISTANT: Sure, may I know your name please?

USER: I am Mark Jones.

ASSISTANT: Ok, please wait for few minutes, let me check with your existing reservation status.

USER: Sure.

ASSISTANT: There is no existing reservation found on your name in our records.

USER: That's ok, thank you.

ASSISTANT: Thank you for reaching us.