ACN Failed product, and refusal to terminate service Concord North Carolina

We set for Internet phone services with ACN several years ago. I passed on the MLM opportunity. Intially, it was great. My wife made calls to her family in the Philippines very cheaply, and we were happy. But, last year the phone system stopped working. We were unable to make or receive calls on the phone. We contacted ACN for service, but were ignored. So, we stopped paying the bill several months after the service failed. Now we are getting harrasing phone calls and have been sent to collections. We have tried to resolve this with ACN, but they have shown no interest at all.