You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I need to change previous reservation due to my planned programme got shifted to another dates so please help me with that.

ASSISTANT: Sure, I will help you in this.

USER: Thank you.

ASSISTANT: May I know your name please for further process?

USER: Sure, please check the reservation with the name of Melissa Martinez.

ASSISTANT: Ok, please wait for a mean while.

USER: Sure, take your time.

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

USER: That's ok fine. No problem, anyway thank you for your time.

ASSISTANT: You are welcome always.