You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I am Sandra Garcia.

ASSISTANT: On which dates you are willing to travel?

USER: I want to change my reservation .

ASSISTANT: Ok, please wait a minute.

USER: sure.

ASSISTANT: There is no reservation found under your name.

USER: That's ok. Thank you for your help.

ASSISTANT: Most welcome.