You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. what can I do for you at this moment?

USER: Will you please change my existing reservation? Because I am shifting my business to other place.

ASSISTANT: Sure, to get your reservation details I need you name please.

USER: Sure, my name is Margaret Clark.

ASSISTANT: We have found reservation on your name. Please help me with your new travelling dates.

USER: Sure, my trip dates are 07/07 - 07/09.

ASSISTANT: May I know your airport codes?

USER: I will start from DFW to reach LAS.

ASSISTANT: Do you have any specific needs for this trip?

USER: I am looking for a connecting flight.

ASSISTANT: Please wait, while  check available flight for you.

USER: Sure.

ASSISTANT: I am sorry to say that we don't have any flights available on these dates.

USER: Ok, thank you for help.

ASSISTANT: Thank you for reaching us.