You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I provide assistance for you?

USER: I am Larry Hernandez, due to my health issues I would like to change my recent reservation which I have done last week to Denver. Can you help me to change my existing reservation?

ASSISTANT: Sure, please wait for a moment to check your reservation status in my records.

USER: Ok, I will wait for your response, but get back with my reservation status.

ASSISTANT: Sorry to say, I did not found any reservation status under your name in my records.

USER: Oh! It's ok, I think my sister already chenged my reservation, anyway thank you for your services.

ASSISTANT: Thank you for choosing us, hope we will get an opportunity to serve you in future.

USER: You are welcome.