You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, which type of service you are looking for?

USER: I am looking for a booking agency to change my reservation due to some health concern, that doctor suggested not to travel in flights. So, can you change my existing booking?

ASSISTANT: Sure, our service provide you such a service of changing a flight ticket with out any cost.

USER: Oh! That's good.

ASSISTANT: Can you please provide your name to check the reservation is existing are not?

USER: John Perez is my name and ticket is reserved on that name.

ASSISTANT: Sorry, I can not find any reservation done on your name.

USER: It's alright, thank you for searching my booking.

ASSISTANT: Thank you for choosing our service.

USER: Most welcome.