Skype plus Bing Rewards
I gave up my landline phone a while back. To compensate, I use Skype for free, even to make calls to mobile or landline phones. That's because I've signed up for Bing Rewards and default to Bing when searching. I use search a lot for work and so my Rewards points add up. Since 100 points gets me an hour of Skype calls, I seldom pay to use it. The combination of Skype, Bing Rewards, and my mobile phone turns out to be a great, low-cost way to make all my phone calls.