Phone service

My home phone through xfinity will either ring once or not at all and disconnect. I've RESET my modem 1,000,000 times.... Every once in awhile, like RARELY it will work completely...other times I am able to make outgoing calls. It is DEFINITELY not the phone itself....I am thinking it's the internet. Ohhh, my cell phone also has decided it cannot call out or receive calls. If this is a TEST, I am FAILING!