You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Timothy Mitchell here.

ASSISTANT: How may I serve you at this moment?

USER: Can you change my flight ticket reservation?

ASSISTANT: Sure, may I know your good name please?

USER: I am Timothy Mitchell.

ASSISTANT: Ok, please wait for few minutes.

USER: Sure.

ASSISTANT: There is no existing reservation found on your requested dates.

USER: Ok, not a problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.