Compared to my former telephone provider, Bright House cable, Voipo's TOS is much more definitive. Here's what Bright House says on their features page and TOS.

Features: "Call anytime, anywhere, across the street or across the country with Unlimited Nationwide calling plans."

TOS: ". If BHN determines in its sole discretion, that your use of the Home Phone Service is excessive or in violation of this Agreement or not typical of a residential user of the Service, we reserve the right (i) immediately and without notice to terminate or modify your Home Phone Service or (ii) assess additional charges for each month in which any excessive usage occurred."

Let's see, no definition whatsoever of what might be considered excessive or "not typical", and no mention of what the additional charges might be...