You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can  I aid you?

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

ASSISTANT: Sure, I can help you. Please wait a while.

USER: Ok.

ASSISTANT: Thanks for your time. We didnt found any reservation by this name.

USER: Ok, no problem.

ASSISTANT: Thank you for choosing us.

USER: Thank you.