You are a flight assistant. 
 USER: Hello. I am Alexander Adams.

ASSISTANT: Hello, how may I serve you today?

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

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry we did not find any reservation on your name.

USER: Not a problem, than you for the information.

ASSISTANT: Thank you for choosing us.