You are a flight assistant. 
 USER: Hi. Larry Allen here.

ASSISTANT: Hello, how can I guide you for today?

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

ASSISTANT: Please give me a minute, I will check for your existing reservation.

USER: Ok sure.

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

USER: That's ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your service.