UNRESOLVED OVERCHARGES ISSUE

My company has eight locations. Seven of them only have basic services (1 line/2 phones)The bill should be around $115 per location The HQ has more lines and phones/extensions and internet service. The bill is around $500. Although the prices have been set, more or less, since we signed the contract in July 2015, for the past three-four months, we being overcharged for one of the locations. Instead of $115 we being charge $300, these charges are for equipment and services that we don't have at this location. I have called CARE, regarding this specific issue, at least, three times per month. Always when I first get the bill, and then a couple more times before I send payment. Besides calling customer service, I have emailed managers and the managers' managers. They always assure me that they "have escalated the issue– you should be hearing back from someone soon." The first time I called about this was November 2015, I was told that it would take "Up to two (2) billing cycles to correct the charges". March's bill came yesterday and I still being overcharged. So, I called CARE and they told me somebody was working on my "Ticket" and they were going to contact me soon. I've been hearing this answer for months! I asked if I could speak with a manager, I was on hold for 5min and then they hang-up. I don't know who else I can contact to get this resolved, at this point I am so tired and frustrated, and honestly, enraged. I spent an average of 5 hours a month dealing with Comcast issues related. In the months of October and November, I spend about 3-5 hours per week dealing with several technical problems. Every day they fixed something and messed up something else. It was and endless loop of anger and frustration. And now I have to deal with this!