You are a flight assistant. 
 USER: Hello, I am Katherine Collins.

ASSISTANT: Hello, Katherine. How may I guide you today?

USER: Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: I will surely help you. Give me a moment to check your details, I will get back to you.

USER: Ok.

ASSISTANT: Thank you for your time, there is no reservation found under your name to do modify.

USER: That's not an issues. Thanks for your help.

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