You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Sandra Nelson.

ASSISTANT: How can I assist you?

USER: I would like to change my existing reservation, can you help me?

ASSISTANT: Sure, I can help you with that. Please be on hold.

USER: Ok, I will wait for your response.

ASSISTANT: Nelson, there is no reservation found under your name to do changes in that.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for reaching us.