You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I serve you?

USER: My name is Christopher perez. I want to change my existing reservation due to my convocation has been postponed. Can you help me with change reservation?

ASSISTANT: Sure, we are here to help you out. Please wait  a while.

USER: Sure.

ASSISTANT: Thanks for your time. We didn't found any reservation by this name.

USER: Ok, No problem.

ASSISTANT: Thank you for choosing us.

USER: Thanks for the information.