You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: I want to change my existing reservation which is done recently due to some health issues, can you please help me?

ASSISTANT: Sure, I will help you with that. Let me know your name to check your reservation?

USER: Sure, my name is Jessica Williams.

ASSISTANT: Ok, please wait a moment.

USER: Sure, I will wait.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: Ok, no problem. I will try with the another booking agency.

ASSISTANT: Thank you for choosing us.

USER: Anyways, thank you for your service.