You are a flight assistant. 
 USER: Hello. I am Ronald Thomas.

ASSISTANT: Hello, what kind of service you are expecting from our side Thomas?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: I feel glad to be your guidance in changing of your reservation.

USER: Thank you.

ASSISTANT: Sorry Ronald, after checking in our booking list I am not able to find any reservation under your name Ronald.

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

ASSISTANT: You are most welcome, thank you for reaching our service. Hope you have a nice day ahead.