When does it become harrassment?

I have received two letters from the USOE in the past three days, in addition to the email I already mentioned. The tone has been unremittantly nasty, continuing to imply that I lied about the number of phone inquiries I attempted, and again claiming that my complaints (aka: whining) has ruined the USOE's relationship with the University of Phoenix. But my questions had nothing to do with the advisement agreement between the two institutions... at the bottom of the web page it says to contact this woman about language skills learned without benefit of transcript proof (or however they phrase non-classroom learning).

I have so far declined to respond to these letters of "apology". I am wondering, however, if I should consult with the U of P or with the teacher's union representative. I feel like these letters are personal attacks, implying that I should have just kept my head down and shut up about my problems. I am so not in the mood to deal with this crazy person. Do I shut up and ignore it, considering that I will most likely not be in this state next year? Or do I reply in a civilized manner, explaining my position? Why do I feel so defensive? I'm pretty sure that I'm not the one who screwed up here...