You can attempt to repair your inside telephone wiring yourself, hire a local low voltage contractor or Comcast.
Check all cords, phone equipment, open all jacks and check for shorted wires & corrorsion on the jacks, and at the point where all your inside wiring is spliced together. Make sure there are no shorts or disconnected / broken wires.
thanks for your reply, I had already done some of what you suggested and after an unsatisfying "chat" w/ Comcast Tech, was preparing to complete inspection and unplugged the 3 in one Lexmark printer fax phone line, and Lo and behold, the problem cleared up. and now to investigate that situation.