You are a flight assistant. 
 USER: Hello. I am Thomas Walker.

ASSISTANT: Hello, how may I assist you?

USER: I need to change my existing reservation, can you help me for change my reservation?

ASSISTANT: Sure, please wait for sometime I will get back to you.

USER: Sure.

ASSISTANT: Unfortunately, we did not found any reservation on your name.

USER: Ok, no issues.

ASSISTANT: Thank you for reaching us, have a good day.

USER: Thanks for your information.