Dear

In my letter of   [date] , I explained that the merchandise
I ordered from you hadn't arrived.  I am attaching a copy of
that correspondence for your convenience.

Having received neither the merchandise nor a response to my
previous letter, I am requesting that you refund the [amount]
remitted with my order.  Attached is a copy of my cancelled
check.

I shall be looking forward to receiving my refund promptly.
Thank you for your immediate attention to this matter.