call ATT and complain, tell them you were w/o access to the net due to being unable to connect for the full day/days including any partial days... and at least get a credit applied to your bill to insure you only pay for what you had access. they can't force you to pay for times you were unable to connect especially when it was due to their problems!!!
i do it every month that they have an outage that i know about in my area.
P.S. while they don't warranty speeds they do have an obligation to provide you with service 24-7/365.. so at least make them credit you the $ for days of service missed.