You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: My name is Emily Edwards. I want to change my existing reservation, due to an accident. Can you please help me for that?

ASSISTANT: Sure, I can help you, please wait for a moment.

USER: Ok.

ASSISTANT: I found you reservation, can I have your details like dates and locations?

USER: My airport codes are IAH and DEN and my trip dates are 04/19 and 04/21.

ASSISTANT: Sorry, I am unable to change your reservation since, there are no flights available.

USER: It's ok. Thank you for checking.

ASSISTANT: Ok, thank you for communicating with us.

USER: Welcome.