You'll need to buy Skype Credit or a subscription to make call international numbers on Skype. Steps to call international numbers from Skype:
1. Login Skype.
2. On the toolbar, select Call-> select Call Phones.
3. Select the country you need to make a call to from the drop-down list. After selecting the destination country, Skype will automatically charge you a fee.
4. Enter the number you want to call.
Or you can also enter a country code manually. To dial country code Angola, You will enter + 244, click and hold the 0 + button for two seconds on the Skype dial pad, then release; the + symbol appears in the Enter number box.
5. Click the blue call button.