Call Forwarding To Verizon Mobile Unite

This has been a recurring problem. I set up call forwarding from my Comcast landline to my Verizon mobile phone. Incoming calls are indeed sent to my Verizon phone but when I pick up the forwarded call, I can't hear the caller. Callers, however, say they hear me. 

Is this a Comcast issue or should I be dealing with Verizon?