Can't Call My Brother

Start with Comcast.  The fast busy on your dial tone is the first indication.  Log in to your primary Comcast account and go to the voice mail section.  Your voice mail box may be full.  There are several pages of settings under the gear icon in the upper right hand corner.  Comcast added several sections of voice settings a few months ago and the default values were inappropriate or not set at all.  You need to get back to your basic normal dial tone.  After you make the changes, be sure and reboot your modem.