Onesuite / Rip off
Onesuite has the complete package for prepaid phone services. When I started using Onesuite back in 2002, it only has the basic prepaid phone card services that you can access online. Then a year after that I remember they added a fax to email feature that give subscribers a fax number for only $1 a month and get their fax through their email. So its like a virtual fax machine and no matter where you are, you will get your fax on your email.
But they didn't stop from there because more than a year ago they added a voip in their list of services with no additional cost. So now if I'm out of the country I can still call back home or anywhere for that matter through voip. If you need a voip incoming calls then subscribe to SuiteAdvantage for $2.95 a month and get a voip number where people can call you. I know a friend who completely dropped his landline and switch to voip to maximize his savings.
These services actually compliment each other because its gives consumers more options to communicate at a cheaper cost of what people are used to paying.
On top of that, I think Onesuite is the only company in the business with 24/7 live customer support which I find it a big plus for people like who only have time to call support of any kind late at night.