Your Cable Company uses Voip. Unbundling your phone will save you money.

Top 3 Residential Phone Services

Ooma $70 one time cost for box, $6/mo. (established 2004)

MagicJack GO $35 one time cost for box, then $2.50/mo.  (est. 2007)

ObiHai / Google Voice $70 one time box cost $0.00/mo (complex transition) (est. 2010)