You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: I am David Rodriguez, due to some personal issues I want to change my reservation flight ticket, can you help me to change that reservation.

ASSISTANT: Ok, please wait a minute, I will revert you back with the status of reservation.

USER: Sure, take your own time.

ASSISTANT: Sorry David Rodriguez, there is no reservation found under your name to change it.

USER: That's fine, anyways thank you for your information.

ASSISTANT: Thanks for contacting us.