Comcast Phone

We are using Comcast Phone.  I am confused.  Is there more than one way to use Comcast phone?

Currently we are using the phone lines in our house and we have a phone line plugged into our Comcast modem.  Is there another way that does not use existing phone lines?  The reason I ask is that we occasionally get 5 minute drops from internet and I was wondering if perhaps noise on the phone line might be causing this modem reboot.