CM500V

I am currently experiencing a problem with Comcast/Xfinity when dialing my Sprint/Samsung (Android) cells phones. When I dial out from my phone, attached to my CM500V modem, I do not hear a ring tone on the handset! It shows the connection time ticking on the handset and it does go through when the cell phone is picked up. Trying to detemine where the no ring tone problemn lies!

Phone: Panasonic KX-TGF340

Modem: NetGear CM500V