You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Mark Jackson.

ASSISTANT: How may I assist you today?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, please wait for a minute to check the reservation details.

USER: Sure.

ASSISTANT: Thanks for your patience, based on your request there is no reservation with your name.

USER: Ok, no problem.

ASSISTANT: Ok.

USER: Thanks for your information.

ASSISTANT: It's my pleasure.