You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can I do for you today?

USER: I want to do some changes in the existing reservation because my friend are not able to join with me on those dates. Can you help me in change an existing reservation?

ASSISTANT: Sure, let me know your good name to proceed further.

USER: I made a reservation by this name Joshua Hernandez.

ASSISTANT: Ok, give me a minute.

USER: Ok.

ASSISTANT: Thank you for your time. Unfortunately we didn't found any reservation matching your name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for picking us.