You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Jack Campbell here.

ASSISTANT: How can I assist you at this moment?

USER: I want to change my reservation due to health issue, can you help me?

ASSISTANT: Sure, I will help you with this.

USER: Thanks.

ASSISTANT: Jack Campbell, there is no active reservation found under your name in our database.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for contacting us.