How does eFax, Google Voice and Skype assign phone numbers to users for free?

So I'm trying to figure out how companies are able to provide free phone numbers to their users like Skype and Google Voice? I tried doing some research on who maintains a list of available phone numbers like ICANN开发者_如何学运维 and found NANPA (North American Numbering Plan Administration). It doesn't look like you can purchase a block of phone numbers from them.

So if I wanted to purchase bulk telephone numbers and provide a service where I could give my users a free number, do I just call AT&T and purchase from them?

Any help or direction would be greatly appreciated.

I'm trying to figure out how I can provide a phone number to my users so I can deliver text messages to them (outside of a cell phone number). Like how users are assigned a phone number from eFax and anyone can send them a fax.

My assumption is that eFax purchased a block of phone numbers from a provider which then assigns to users to receive fax messages. If you own the number, the routing should be fairly simple.

So maybe the direction is to provision the number in real-time as users sign up and pay that fee (whatever it may be).

I'll check out your link to bandwidth.

Check out http://www.bandwidth.com or http://www.voip-info.org/wiki/view/Bandwidth.com.

Bandwidth.com has an API for real-time provisioning. I'm not sure about the cost though.

Essentially, you don't even have to purchase them. You just need to be a (registered) telephone company. That's a bigger burden than you probably expected, but I expect Skype and Google did this. For smaller companies, it may be wise to outsource this, but you'd want to find a partner that isn't competing with you. AT&T wouldn't sound like the best partner if you're going to sell VOIP to consumers.