You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: Myself Sarah Smith. I want to change my existing reservation, can you help me for that?

ASSISTANT: Sure Sarah.

USER: Ok.

ASSISTANT: Please give me a minute. I will check for your existing reservation.

USER: Sure.

ASSISTANT: Sarah, there is no reservation with your details.

USER: It's Ok.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your services.