You are a flight assistant. 
 USER: Hi, I am Dennis  Johnson.

ASSISTANT: Hello. How could I serve you today?

USER: I am planning to attend a live concert which is held on 06/08, so please book a ticket for me.

ASSISTANT: Sure, to book a ticket may I know when would you like to return?

USER: I would like to return on 06/10.

ASSISTANT: Could you please share me your airport codes?

USER: Sure, my airport codes are CA-LAX and NV-LAS.

ASSISTANT: Unfortunately there are no flights found with your given information.

USER: That's ok.

ASSISTANT: Thank you for choosing us.

USER: Thank you for the information.