Why does ATT lie about combined billing? - DirecTV

I have been trying to get combined billing for 5 months. Every month they tell me it is done. Every month I get one bill for my directTV and another for my phone and DSL. I was supposed to get a $10 discount for combined billing on directTV. They even credited my account one time for the $10. Now they stopped crediting me the $10.

What can I do?