Misrepresentation from ATT rep

Decided to go with another carrier after I have used ATT for 6 years.  On July 16, 2014, I called ATT and spoke to a representative and I asked whether I needed to cancel on or before the final day of my billing cycle (the 17th of each month) or if I were to be prorated when I do cancel my service.   The ATT representative told me I would be prorated since I was not under a contract.  On 7/22/14 I cancelled my service.   Today (7/25/14), I called ATT to find out why I still had service.  I was informed that there is no prorating and I would be charged $125 for the next billing cycle.  I also found out that the ATT representative who told me that I could cancel and have my bill prorated no longer works at ATT.   To me, $125 is a lot of money that could buy me quite a few rounds of ammo.  Very dissapointed.