Dear Felix
I regret that we have had a less than satisfactory experience with [NAME, ex. Alicia Johnson], whom you sent to us as a temporary [POSITION, ex. secretary] on [DATE, ex. June 10]. [STATE NATURE OF DISSATISFACTION, ex. Her curt nature of dealing with customers on the phone resulted in three separate complaints made to me by displeased callers.] {Unfortunately, I was forced to let her go [TIME, ex. after the first day]}.
Since I know your firm to have reputation of providing decent services, I am confident my experience is merely an uncommon aberration. Nonetheless, I trust this information to be useful to you.
Regards
Lydia