Samsung Galaxy S4 (GT-I9505) is the first in the series to have inbuilt Internet calling facility to use your VoIP to place Internet calls. This is really a wonderful feature to save money on your international calls.
The internet calling feature can be configured at
Settings>>My Device>>Call settings>>Internet call settings
You can add much as SIP accounts that you would like to use for internet calls. The settings are very simple, you just need to enter username, password and sip server. Additional settings may require for some SIP providers. You will be able to use internet calls for all calls or for selected calls.
Please leave a comment if you would like to know how to configure your VoIP provider SIP settings on Galaxy S4, your Life companion.
See the video for detals