I have vonage phone. $24.00 per month no long distance charges anywhere in US. Works well most of the time. Sometimes I get echo, a few times one direction gets bonkered so I can not hear the calling party, usually just requires recalling the person. This is very occasional. Other thing is if cable company goes down then the phone does not work. But for the price I can live with a few glitches. I can call any numbers, i.e. cell phones, other voip users or standard telco.
The only equipment needed is a small modem that plugs right into router.