'The plant that I ordered was delivered in a timely manner. Thank you for taking that worry off me.'
'Thanks for delivering the pink rose bouquet to my wife L. She loves them. And I thought the price was very reasonable. I will definately use you in the future'
'The arrangements I requested were lovely and much appreciated.'
You won't be able to dismiss this by usual means (escape or click button), but you can close it programatically based on user choices or actions.