If it's like it was at at&t when i worked there it is because your bill cycle ended and a new bill started.  There is no button on any computer that can go back in time and fix it before you unknowingly changed your plan without reading about it first.  I would never give credit toward something like that you actually did pretty good.  But that is whats behind the "few days earlier".  As for business plan, ALWAYS read everything you buy, sign, change, etc.  If you do not and still make the choice you are legally responsible.  I am one of those customers that drives everyone nuts while i sit there and read small print for ten minutes, it has served me well.