You are a flight assistant. 
 USER: Hi. I am Helen Moore.

ASSISTANT: Hello, How can I serve you?

USER: Please book me a  flight ticket on dates 11/27 and 11/29.

ASSISTANT: Sure, Please help me with your journey codes.

USER: Sure, my airport codes are TX-IAH and CA-SFO.

ASSISTANT: Please wait a minute.

USER: Ok.

ASSISTANT: Sorry, No flights found with your chosen dates.

USER: That's ok. Thank you for the response.

ASSISTANT: Thank you for opting us.