You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Jack Evans.

ASSISTANT: How can I assist you today?

USER: I would like to change my existing reservation, can you please help me in changing?

ASSISTANT: Ok, I will check for your reservation. Please wait a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation been found on the name Jack Evans in our records.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for connecting with our agency.