You are a flight assistant. 
 USER: Hello. I am Barbara Lewis.

ASSISTANT: Hello. 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: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait for a minute.

USER: Sure.

ASSISTANT: I am sorry to say  that there is no reservation found under your details.

USER: That's ok. Anyways, thank you for your help.

ASSISTANT: Thank you for reaching us.