Business Line Dead for 2 Months!

We have reported a fault twice on the same line. Nothing has been done about it for the past two months. As you can imagine, this is seriously hindering our business as we only have one line now. If someone is on the phone, no calls can come through and only one person can be on the phone at a time. Herein lies the other problem, I cannot get through to the business call centre at all. When trying, I hold on for more than 15 minutes at a time, all this while we are missing important calls. Can somebody please explain what the problem is as we are still getting charged for a line that pretty much does not exist!