You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you now?

USER: I am Margaret Robinson, can you help me for changing my existing reservation?

ASSISTANT: Sure, I am ready to help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment.

USER: Ok, I will wait for your reply.

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

USER: Oh! I think my sister's already changed my reservation, anyway thank you for your services.

ASSISTANT: Most welcome. Thank you for choosing us, have a great day.