Switch from Cable, get $100, got $50 instead

signed up for att dsl also with an offer of $100 rebate for switching from cable. I received a letter in the mail telling me to go to att.com/rewards to get my rebate. The $100 rebate wasn't there, but there was a $50 rebate, so I clicked on that one and it says it is being processed. I called the att reward center and asked how I could get the $100 rebate and they told me that since I had claimed the $50 one I couldn't get the $100 one. I explained it to the rep, their supervisor and the floor manager and they said since I had clicked ther terms and conditions for the $50 rebate I wasn't eligible for the $100 rebate. I asked if they could fix it and they said NO, I asked if they could fix it some other way, like a bill credit and they said NO. They basically blamed me for clicking the "agree" button on THEIR rebate center web page; and did not even acknowledge that there was a problem with their rebate system.