Provided exemplary service...
I worked with [your customer service representative] for several months on a memorial for my late wife (and me). A headstone is probably the last thing I ever thought I would buy on-line/mail order, but [you have] provided exemplary service and exacting information that made a complex long distance transaction seem much closer and easier.
[You] corresponded by phone and e-mail and sent photos on a regular basis. [You] always made sure that I was aware of the current status of the order. [You] offered helpful advice and forwarded information from the designer and shop foreman. [You] coordinated the shipping and installation in Utah.
[Your customer service representative] is a credit to your company and I want to let you know how much I appreciated her efforts. The monument turned out very nice. The designer and craftsmen are to be commended.