Incorrect charges on bill and cannot get it corrected!

I have called Comcast several times about this issue.  I received business services over a year ago and had to close my business.  Since Comcast wanted to charge me an early penalty of over $1,0000, I transferred the service to my home and set up a home office that I really did not need.  Of course, the bill doubled for the remainder of the contract. When the services was transferred, they charged me double the amount I was quoted.  I keep calling and keep being told it would be corrected.  The last representative told me the pay the $300 incorrect charges until It was credited on the February bill. Of course, it was never credited.  I am totally frustratedwith dealing with this issue.