Fongo ATA $49
Webslinger is the official Redflagdeals voip guru, so for details... read his posts!
In 2016, I don't think it's worth it to keep paying $20-40 a month just so your dentist or doctor can leave a message on your answering machine.
Do the math, switching to voip offers a great ROI
If you're looking for a simple solution to switch to voip, especially if you have children at home or health issue (you need 911), Fongo home and Ooma are worth looking at.
If you're tech savvy, FreePhoneLine.ca and voip.ms are better solutions.
Finally if you're looking for free calls with friends or family, many apps do offer that like like Viber, Skype and Messenger.
My setup: outgoing calls with Google Voice (free), incoming voip.ms (one single phone number at home (Obi 202) and on my cell phone).