If you have a good AT&T cell signal try At&t wireless home phone service. Unlimited nationwide service $ 20.00 per month. I have been using it for a few years. With go phone version it is a flat $20 no extra taxes. Some states add a 911 fee. Just purchase the receiver box ($79.99) and port your number and you good to go.
Although Sibley's already got a solution, since it's been brought up, I might as well respond.
This is only a marginally decent deal, and only for people who don't have sufficient or stable broadband access to do VoIP on. There's also cheaper ways, such as a used AT&T carrier locked ZTE WF720 units (seriously, like $10 or less dirt cheap) that can be paired with nearly
any AT&T MVNO's SIM card for making and receiving calls. If you know how ridiculous "unlimited" phone plans are, you can easily get under $20/month on this end using any of the AT&T MVNOs from the guide. Even a "trivial" amount of time like 1000 minutes is 16 hours and 40 minutes of talk time a month, or an average of 30 minutes of talk time a day. 1000 minutes seems like far less time when it isn't measured in hours, doesn't it?
Even today, most users rarely exceed about 700 minutes of talk time a month on their cellphones with no home phone... and that's considered a heavy user by the industry. Most people just don't call much anymore... it's all text messages and IM clients.
If you want a GSM carrier unlocked device, the thing to search for on Amazon or Ebay is a "fixed wireless terminal", and GSM 850/1900 units (what you need in the US) can be had new for under $60, then you can use any T-Mobile MVNO you like for equal or cheaper than $20 a month as well. I'd say you could use these carrier unlocked terminals with AT&T MVNOs, but these aren't UMTS 3G devices and AT&T is pulling the plug on their 2G network, but T-Mobile is keeping their 2G support around.
If you only need/want one singular phone in the house going this route, there's also GSM desk phones that can also do texting if that sort of thing floats your boat. There's plenty of these things available for less than $60 as well.
There's also cheap, used fixed wireless terminals from Verizon available on Ebay that can be activated for $17 a month for 1000 minutes on Selectel.
Just pointing this out for those who can't do VoIP for some reason, but are considering home phone service of some stripe. As always, there's cheaper methods than AT&T when you know what's available.