You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello,. How can I support you?

USER: My trip to Dallas has been postponed, due to the heavy rainfall and thunder storms. So, Can you change my existing reservation?

ASSISTANT: Sure, please provide your name?

USER: Thanks for your response. I am Benjamin Smith.

ASSISTANT: Sorry Benjamin Smith, there is no active reservation on your name.

USER: That's ok, I think I have reserved my ticket with another airlines. I will recheck my details. Thanks for your effort.

ASSISTANT: Thanks for approaching us.