You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Thomas Adams.

ASSISTANT: How can I assist you?

USER: Can you help me for changing my existing reservation, because I am unable to travel at this moment due to health issues?

ASSISTANT: Yes, I can do that for you.

USER: Thank you.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Oh! It's ok, no problem thank you for your services.

ASSISTANT: Thank you for reaching us.