You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Jack Wilson here.

ASSISTANT: How can I help you?

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

ASSISTANT: Sorry, there is no reservation found under your name.

USER: It's ok, no issues.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your help.