For my AT&T cell phone bill, my bill payment due date is usually 15 days from the bill closing date. For example, if the bill period is 12/14 to 1/13, my payment due date would 2/2. They now changed it so that if you are paying by credit card, your payment due date is within 6 days.
For this month, my bill period was 1/14 to 2/13 and my bill due date is 2/19 and if you want to keep the 3/2 due, you have use your debit card or checking account.
It looks like AT&T gets money late when credit card is used. With Debit card or Checking account, they get the money quickly. If I were to run my business, its reasonable to expect the money right away after providing the service.
For more info look at this