I would guess that there are a lot of options. For instance you can get these types of services, most of which are based on voice over IP or Internet telephony, http://cheapdslinternet.com/cheap-home-phone/. Of course that has a few problems, the first of which is that you are not going to be able to stick it in your pocket and take it with you. I know a few people who use really cheap phone services for cell phones. The most famous kinds are the Smart Talk system that you get from Wal Mart and a Trac Fone, both of which are disposable systems. I remember that they used to talk about this stuff on the HBO tv show The Wire, which was one of my favorite shows ever. Obviously that was a cops and robbers shows, or cops and drug dealers. The drug dealers would buy dozens of these types of phones and use them until they ran out of minutes then dump them. They called them burners in the show.
I was looking at the Trac Fone because this guy was telling me that his cost him around 13 dollars a month. The problem with that is that this guy was not telling any people what his number was. The only way that his phone was that cheap was because he was only using it for brief conversations. A normal person would have a girlfriend or a boyfriend that they would take to all of the time and two or three friends who were always calling them up for no reason. He does not do that sort of thing if you call him up he will politely tell you that you are burning up all of his minutes if you do not get to whatever the point of the call is.