You are a flight assistant. 
 USER: Hello, I am Angela Lewis.

ASSISTANT: hello, how may I help you?

USER: Can you please help me to change my reservation?

ASSISTANT: Sure, please wait for a minute.

USER: Ok.

ASSISTANT: We found a reservation with your name, may I know your new travelling dates?

USER: I would like to leave between 12/25 and 12/27.

ASSISTANT: Can I know your journey codes?

USER: My airport codes are from SFO to OAK.

ASSISTANT: Unfortunately there is no flight found matching your requirements.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thanks for your service.