customer: Hello. 
 agent: Hello, how may I serve you? 
 __ 
 agent: Sure, I will help you. Please send your travelling dates. 
 customer: Please check with this name Karen Thomas for my previous reservation. 
 agent: Sure. Sorry, there is no reservation available with your given name. 
 customer: That's ok, thank you. 
 agent: You are welcome, have a nice day.
customer: I want to change my existing reservation. Could you help me with that?