Vonage has introduced Vonage Mobile app that saves more than 50 percent on international calls to dozens of countries. The VOIP based free app for iPhone and BlackBerry uses cellular or WiFi networks to make international calls at incredibly low rates.

The Mobile app works with your existing mobile calling plan, so you keep your number and existing contacts. Simply download the Mobile app and set up your account based on your present number. When using the cellular network, Vonage users will use up minutes from their cellular network plan. However, Vonage says that consumers will still save a lot on international calls because they will pay Vonage’s lower international rates rather than those of cellular network.

Vonage also said that the iPhone and BlackBerry apps work differently. For example, iPhone users will have to open the Vonage app to take advantage of its cheaper rates, whereas BlackBerry users will automatically revert to the Vonage rates over the wireless provider’s every time an international number is dialed.

You can learn more and download the Vonage Mobile app for iPhone from iTunes.