CANNOT HEAR FORWARDED CALLS

My home Comcast phone has been on call forwarding to my cell phone for many years and I have had no problems.  Recently I have been unable to hear any calls that are forwarded to me - they can hear me but I cannot hear them.  I have learned to instruct them to call my cell phone directly in order to reach me.  I'm wondering why I still have this service since it no longer works for ANY purpose.  Is anyone else having this problem?