I am getting billed twice a month

I am new customer.  I signed up for a promotional offer of $19.95 per month.  My first bill ($100 for the Internet Gateway and first months fee of $19.95 was due 9/9/14.  I set up an automatic payment for 9/9.  On 9/3, I received my second bill.  It said my first bill was LATE, then said my next payment of $19.95 was due 9/23/14, just two weeks after my first bill.  I called and complained; AT&T said they would change my due date back to the 9th of each month.  I set up an automatic payment of $19.95 for 10/9/14.  Third bill:  New due date is 10/12, BUT I was charged $9 late fee for not paying on 9/23, then charged $9.97 (half month).  So my Oct payment is $19.95 + $9.97 + $9 Late Fee.  I called and complained; AT&T said they would drop the late fee and correct the partial months charge.  Fourth bill arrives:  This one due 10/23.  Includes all previous charges, plus another $9.97 for half a month, plus another $9 Late fee.  Fifth bill arrives.  This one due 11/07.  Added $15.29 for 3 weeks of service, plus another late fee.  THIS IS CRAZY.  I paid $19.95 in Sept, Oct, and have an automatic payemnt set up for 11/07.  But after paying that, I will still be "owe" $33.28 in late fees and "partial months".  I refuse to pay more than $19.95 in a calendar month.  If AT&T thinks the can take more than $19.95 a month from me by squeezing my due dates together, they are mistaken.