Customer service for billing question

How the heck do you reach anyone for a billing question? This is on our business wireline and there is an extra charge on our bill with no explanation. They just made an adjustment, with no details, and now are showing we are past due for the adjustment. How can we be past due when we paid our bill on time with autopay? We never got a notice that there was an additional bill.

 2 days in a row I have called the number on our bill. The automated system states the approximate wait time to be 3-4 MINUTES. Both times I have been on hold for over 4 hours without speaking to anyone. I cannot have them call me back because we have our own automated system so the call back will not come through. What do I do?