Mediacom Phone Service

I signed up for Mediacom phone service to go along with my internet and cable service. Mediacom was here on 1/24/08 and "hooked" me up. I can make outgoing calls, but am unable to get incoming calls. I run a small business and have lost nearly $8,000 since last Thursday. Mediacom says they are "working" on it since then. I finally spoke to a supervisor today and he said that he would be in touch with me via my cellphone by 4:30 om today. They have no idea what the problem is much less how to correct it. I will be re signing with y old phone company tomorrow at 8:00am. Mediacom is the worst company in history as far as customer satisfaction and customer service.