Voxofon for iPhone/iPad - Voxofon is a mobile app that allows you to connect with all your friends and family anywhere in the world using your iPhone, iPad or iPod touch. With it, you can make voice calls and send messages for free to any other user who has the app installed
UppTalk for iPhone - UppTalk allows you to keep in touch with all your friends anytime, anywhere. With it, you can make free calls, send free SMS and chat for free from your mobile phone.
Whenever you are called or you receive SMS to your UppTalk number, and when you install the app or invite friends, you receive Energy
3CXPhone for Phone System v11 (iPhone/iPad) - 3CXPhone is a SIP client for the 3CX Phone System that allows you to make and receive VoIP calls from your iPhone, iPad or iPod touch. Calls are made over the internet instead of the mobile network, saving on costs
yuilop for iPhone - Yuilop allows you to keep in touch with all your friends anytime, anywhere. With it, you can make free calls, send free SMS and chat for free from your mobile phone.
Whenever you are called or you receive SMS to your yuilop number, and when you install the app or invite friends, you receive Energy
MobileVOIP is a free iPhone calling app which lets you make (free) national or international voip calls directly from your iPhone. You can save on your Mobile Phone costs by simply installing the MobileVoip app. Select any contact from your contact list which is accessible in the app and start your call using MobileVoip anywhere, anytime
Voypi for iPhone - Don't you wish that your phone calls and text messages were absolutely free? With Voypi you can call or text to other Voypi users anywhere in the world absolutely free. No ads. No catch.
Voypi is super easy to use. It works with your phone's contact list so you won't need to change anything in the way you call or text friends
AVT Mobile - AVT Mobile is a convenient way to make cheap international calls. No need to memorize international numbers, or scratch cards. No need for WiFi or stable 3G. All you have to do is choose your international destination number and AVT Mobile will make a local call instead. It's that simple!
Please note that AVT Mobile is not a SIP application