You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Sarah Miller here.

ASSISTANT: How may I help you?

USER: Reserve a flight ticket that is from CLT to DEN.

ASSISTANT: Please provide me your journey dates.

USER: My preferable dates for travel are 05/13 to 05/15.

ASSISTANT: There are no flights available at this moment.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you for reaching us.