You can word it something like this:
To Whom It May Concern:
I am writing this letter in regards to work I recently had done by ______( name of the company). I would like to extend my appreciation and grattitude towards ______( name of the company) for a very professional and wonderful job. In the future, I would be more then glad to be a reference for future business contacts and future jobs. Please feel free to contact me at your convienience.
Sincerely,
( Your Name)
Hope this helps! Good Luck
To Whom It May Concern:
I am writing this letter in regards to work I recently had done by ______( name of the company). I would like to extend my appreciation and grattitude towards ______( name of the company) for a very professional and wonderful job. In the future, I would be more then glad to be a reference for future business contacts and future jobs. Please feel free to contact me at your convienience.
Sincerely,
( Your Name)
Hope this helps! Good Luck