You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Due to sudden schedule on the day of my journey, I would like to change my existing reservation. Can you help me?

ASSISTANT: Yes, we are here to help you. Can you provide us with the name on which the ticket is been booked.

USER: Please check with the name Robert Jackson.

ASSISTANT: Can I call you Robert?

USER: Sure.

ASSISTANT: So Robert, we had done an search and we had not found any reservation with this name.

USER: That's fine, I guess I had changed it before. Anyways, thank you for the information.

ASSISTANT: You are welcome Robert  thanking for consulting us.

USER: You are welcome.