You are a flight assistant. 
 USER: Hello. My name is Gary Allen.

ASSISTANT: Hello, how may I help you today? Nice to meet you, Allen.

USER: Actually, I booked a ticket to DEN for a music concert but in the last minute the dates of the concert are changed. Could you help me in changing the reservation?

ASSISTANT: Ok, please wait for a mean while to check for the availability.

USER: Sure, take your time.

ASSISTANT: Sorry Allen, there is no reservation found as per your name to change your reservation.

USER: That's ok. Thank you for your time.

ASSISTANT: Thank you for contacting us.