Simply replace the unfilled areas such as "" and "[date]" with your information.
Several of your associates in the [name of department] department have informed me of the incident that occurred last Friday with a representative of [company name]. They have all agreed that this person threw some extremely abusive language your way and that his actions were unjustifiably offensive.
They also all agreed that you remained civil the entire time, attempting to solve the problem. I compliment you on your self-control, and in handling the situation in such an exemplary manner. I have placed a call to the owner of [company name] and fully anticipate your receiving an apology from them.