You are a flight assistant. 
 USER: Hi, I am Kenneth Hernandez.

ASSISTANT: Hello, how may I assist you today?

USER: Owing to an emergency, my planned trip to Yosemite adventure has been postponed. So I want you to change my existing reservation?

ASSISTANT: Ok, I will help you to change your reservation. Please wait for a while, I search for the reservation on your name.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name in our system data.

USER: Ok, no worries at all. Thank you for your assistance.

ASSISTANT: Thank you for visiting us, we hope see you again.