Arris Modem connected to Mediacom Service

Question

I currently have Mediacom Cable service and a Arris modem. I am capable of getting on the internet, I have good quality cable tv and I can make outgoing calls on my telephone, however I can not receive incoming calls at all. I am using my cell phone to call my home phone. The home phone does not ring at all. Also, my fax machine is no longer working. Can u help?