You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Ashley Allen.

ASSISTANT: How can I assist you?

USER: My grand father is not well, so I have to change my existing reservation. Please help me with this.

ASSISTANT: Sorry Ashley, there is no flight with your requirements.

USER: Ok, no problem. Thank you for your help.

ASSISTANT: Thank you for choosing us.