'Thank you for your reliable service. So much appreciated.'
'It's is the first time I use this company and I have to tell you service was extraordinary. Thank you from the bottom of my heart it meant a lot to me that the arrangement get delivered on time.'
'I have been impressed with your service, and would recommend your website to friends and family. Thank you, also, for the timely emails.'
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.