Your smartphone is chock full of exciting features. Unfortunately, you'll pay big to use them.

You don't have to cut back on your phone's services for fear of a giant monthly bill, though. There are plenty of apps that can help you save on the features you love.

Viber allows you to make free calls with your existing phone number. No registration or login is needed.

It uses cellular service or Wi-Fi, so you choose which works best for you. Although you can make calls only to existing Viber users, the app boasts 40 million users.

Another app that's great for free calls is Skype. Unlike Viber, you can place voice calls to people who don't use Skype, but there will be a small fee.

The app works just like it would on your computer. In fact, you can place a call to a computer - not just other smartphones - with the Skype app. If you don't feel like talking, Skype offers instant messaging features at no charge.

One thing Skype can't do on mobile devices is video conferences. That's where Fring steps in - it allows you to host a video chat with multiple friends at no charge!