I use Viber, an app which is similar to Whatsapp but with a feature that u can make viber to viber free calls a lot. There wasn't any standalone software for windows but now they released an official software for windows. You may use this one now as an alternative for Skype.
where and how to download?
You can download it straight from their
official website. Before using viber in your PC you need to have viber installed on your phone. Once you installed the app in PC, it will ask your phone number. It will sent a text message code to your mobile viber, which will used to activate or verification purpose.
After you done everything, Viber will sync with your phone to import the contacts on your PC. Now you are ready. Just make a calls and chat with someone you want to.
The best feature this PC version is this allow you to transfer the ongoing call to your phone. All you need to do is just tab the "Transfer call" and Viber will run automatically into the task bar which makes easier to get the calls and messages easily without miss any !
Have a try and give your feedback of the app guys.