If you would like to complement someone on their customer service, here is a sample commendation letter template you can use to write a customer service thank you letter.
To,
[Staff name]
Dear [Name],
It gives me immense pride and pleasure to congratulate you for your commendable customer service for the past [year]/ [number of months]. We have reached an extremely high percentage of customer satisfaction, all because of your praise-worthy performance.
We appreciate your dedication and would request you to keep up the great work.
Thank you
Sincerely,
[Your name]