The final step in getting the results you want may be to give up and go somewhere else to get your business taken care of. Although that is not an optimal solution, in some cases it is all you can do. If you are not being treated the way that you deserve to be treated, then that company is obviously not worthy of your business. If no one works with you to try to rectify your situation, then you have done all you can do, and it is time to make good on your promise to take your business elsewhere. Many customers threaten to go somewhere else when they are treated poorly, but then return to the same place of business to be treated poorly again. This only decreases the likelihood that anyone will take your complaints seriously in the future. It would leave a much larger impact on the company if you take your business elsewhere, and then send the original company a copy of your paid bill with a letter explaining how you could not get your issue resolved, and this was how you finally chose to handle the problem.
No matter what, you as a consumer need to be treated fairly and with respect, and if there is a company out there who is not doing that, then they absolutely do not deserve your patronage. If you cannot feel 100% satisfied with what you are receiving, then take your business and your money somewhere where you can feel that amount of satisfaction. Remember that no one at any company will be able to treat you poorly if you do not let them!