You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Sandra Evans.

ASSISTANT: How can I assist you today?

USER: I want to change my travel dates in my previous reservation, can you please help me with that?

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

USER: Oh! May be I am not booked my ticket properly at that time. Thank you for your service.

ASSISTANT: Welcome, have a great day.