You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Joshua Thomas.

ASSISTANT: How can I assist you?

USER: I would like to change my existing reservation due to my plans to visit Dallas got postponed. Can you help me with this?

ASSISTANT: Sure, please be on hold.

USER: Thank you.

ASSISTANT: There is no reservation found under your name to do changes in that.

USER: Ok, not an issue. May be something went wrong while making the reservation previously. Thank you for providing information.

ASSISTANT: Thank you for choosing us.