How long does it usually take for the final bill with the ETF to show up?

Hello,

  I just cancelled my ATT wireless service on Jan 1st. When I look under my account it does show status " canceled Jan 1st" But it does show my amount due is $80.00  due by Jan 19th. Now will will the bill just be adjusted to show the ETF when the time comes or are they expecting me to pay the $80.00 for serivce then bill me AGAIN with the ETF? I do not want any kind of late fees and I would like to go ahead and pay my total bill ASAP and not one bill now and then another later. If someone could help me out with the answer to this question I would appreciate it.

Thanks.

-A