A few years ago, we made an extensive list of 60 free VoIP services. Okay, so it was 58 free VoIP services – and some weren't VoIP services but free VoIP technology – but the important thing is that there are lots of free VoIP services out there. And the important thing to know about free VoIP services is that they offer free phone calls.

Free VoIP services tend to come and go, too, especially those from our favorite free VoIP service nemesis (or is it nemeses) the Betamax Group. Since Betamax still gives people trouble (customer service is non-existent), we thought we would put out a short primer on how to make free phone calls using free VoIP services.

The most important thing to ask when trying to make free phone calls is: Which type of free VoIP service are you going to use to make a free phone call?

There are three basic ways to make free phone call:

• Free In-Network Calls
• Free Trials
• Not really free calls

Free In-Network Calls are the most common way of making free phone calls using VoIP.

Basically, the majority of costs incurred on phone calls comes when different networks have to exchange calls. When you call from one network to another, your phone company has to pay the owner of the other network to complete the call.

But, if a call can stay in-network, you can call for free. This is how Skype allows you to make free phone calls to other Skype users. This is also how CallCentric's IP Freedom calling plan works and it's how Fring and countless other VoIP services work.

The disadvantage of this calling method is that it costs you money to call out. If you want to call someone who isn’t on your network, you've got to pay. You can still get cheap phone calls – just a few cents a minute – but that's not free.

A free trial is another way that you can make a free call using VoIP phone service. The one catch is that a free trial assumes that you're going to be paying to use the service – eventually.

Sometimes, free trials aren't as free as you think they are, either. If you're looking to make free phone calls during a free trial, there's usually a limit on the number of calls that you can make in a month. Make sure you check the terms and conditions of the phone service before you try it.

Also, with free trials, you often have to make some kind of commitment to the VoIP provider to get free phone calls. You can always cancel but termination fees and activation fees might come into play. Again, check the terms and conditions before you try the free trial.

The first two methods of making free phone calls are, despite their limitations, ways to make free phone calls. With in-network calls, you can just stay in the network and call free and clear. With a free trial, you just need to make sure that the trial stays free, by being aware of what will make the trial NOT free.

There are other VoIP providers that say they offer free calls but the calls aren't free!

Betamax is a great example of fake free calls. Betamax offers free calls and free calling days on whim; if you can catch a Betamax company on a free calling day, you won't have to pay anything. However, there are ton of hoops you have to jump through in order to get a free calling day.

You also get free calling days if you purchase credit (which is what you would do if you were using a service like Skype or Fring and bought credit). These credits expire very quickly if you don't use them and they can expire if you don't keep your account topped up. You can see more details of Betamax's free calling on our betamax page.

The other not really a free call VoIP service is from Google Voice. As you may have heard, you can all any United States number for free with Google Voice.

This is free, with no strings attached. However, other international destinations are not free, calls can only be made from a computer, and free calls in the United States only work as long as Google subsidizes the cost of the calls in the United States. So, when it ends, it ends.

However, if you're interested in riding the free Google gravy train as long as possible, you might as well check out TelTub. They offer an adapter and service for Google Voice – called gHome – that allows you to turn Google Voice into a home phone system.