Online Bill Payment disaster

USA Resident

Why/how can my payments towards UVerse account be redirected to an old wireless bill that has been turned over for collection and is no longer visible on my account when I sign in to MYATT?   I called the customer support number, and tried to explain that I make online payments all the time and the funds are directed correctly until august and September when the process broke.  The agent was not helpful and seemed more interested in telling me it was my fault that the bill did not go where I intended.  Then she had me call the wireless dept and ask them to redirect the payments back to Uverse.  Wireless said they could not do it, Uverse would have to initiate.  in mean time 2 payments totaling $585 is out there in limbo, my service has been cancelled and no one can or will help me.  I have been an AT&T customer for about 18 years and this is very, very disappointing to me.