This.
The one, true way you can come out smelling like roses in any kind of retail transaction dispute is put all emotion and drama aside, and speak in a calm and business-like manner. Especially in electronic communication, the need for leaving out any hint of irony, humor, sarcasm, etc is so important - unless the person knows you well, a phrase that would cause both of you to chuckle if you were eye-to-eye can easily be misconstrued. Be plain, speak facts, get stuff accomplished.
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