My yearly billing fiasco

I have a 4 line business account in a busy doctors office. I received a bill this month for 698.90 normally 362.89. I called they said my discounts had expired. They said I was sent a letter that I never received. This office also receives 1-2 calls per week from resellers representing themselves as ATT. This is not only annoying but waste my staff's time and we can't discern whether the calls are legit or not. They all say we need to change this or that or your contract will change etc. Anyway I was told that my bill would basically revert back to roughly what is was but they would only be able to refund the over charge after being reviewed by a supervisor and I would receive a call back in 1-3 hours. Never happened. I also e-mailed small business support, which I previously had good results, was given an automated answer and was assigned a case number 40278733. The message said they would research and send me a resolution. No answer. I can see by reading other people on this forum that many calls get made with no help.  It seems like every year or two that I have to go through this. This office is very busy and don't have time for this stuff. Can't I just get my bill every month and pay it. If you insist that we interface with ATT every year, then you need to make it more user friendly and efficient. Nobody has time for multiple phone calls to accomplish a simple task. Please Help