VoipRaider is a free Android app that allows you to save on your monthly calling charges by up to 80% by making cheap or free international calls through WiFi or 3G networks. It offers the lowest rates available for destinations that aren't free, making it an ideal option for those looking for a cheaper telecom provider. You can choose any contact from your regular contact list or add new contacts and even import contacts from your VoipRaider client.

To start saving, you need to download the free VoipRaider dialer app, register a username or log in using your existing credentials, and buy some credits. With VoipRaider, you'll get the first 90 days of calls to selected destinations for free after buying 10 euro credit. You'll only start using your bought credit after these 90 days have expired. Additionally, you can use your credit for any calls to non-free destinations, and you can even send SMS Text messages to any mobile phone for the lowest tariffs.

Please note that using the app as a default dialer may interfere with dialing 911 emergency services.

Overall, VoipRaider is an excellent option for those looking to save on their international calling charges with its low rates and free 90-day trial offer.