I have been using Zoiper free version on my Iphone for over a year now. After updating to the current version v.3.15.2 from 3.14, outgoing calls always cause the app to hang. Basically pressing the call button after inputing any number on the dialpad causes the call button to change color to blue from green and the app will just hang and do nothing. Calling from history also causes the app to hang. Incoming calls still work fine though. I have another Iphone with v3.14 still on it. That one still works fine for both incoming and outgoing calls.