#1 - It's not possible that the taxes got screwed up.
#2 - It's hard to determine what exactly happened with your description of the situation. Computer rebates in the packages are very complicated, that's why mail-in rebates will soon be a thing of the past (thank goodness).
http://news.yahoo.com/s/zd/20060126/tc_zd/170077
#3 - Don't call the corporate office, call the district office. I'm not real familiar with the Texas stores but if you can tell me which stores you were dealing with (hopefully with stores #'s, they should be on your receipt), I will PM you the phone # for your local district office.
Very sorry you had difficulty with your shopping experience.