I guess it's just an issue pertaining to Serbia (or maybe I'm doing something wrong?). No service works here unless they specifically mention they do. It's a frustrating thing :)
For now, I've reset your trial call limit and it should work for you.
I'll also be sure to recommend you to people I know are having this specific difficulty of poor call quality with Skype or Viber. That's a great service you've got there, and keep up the good work :)
Of course many countries are not nearly so much. I also do plan to add voip calling within the app. This would allow you to skip the high cost of crossing Serbian boundaries when you're near a decent internet connection, but give you flexibility to make calls directly over the PSTN when needed.
1) I have to use Safari instead of an app, so it can't interact with my phone's address book. So I have to copy-paste the two phone numbers.
2) I almost always have to log in each time I use it, because the auth session has timed out.
3) I have to zoom in/out as it's not mobile optimised.
If you could offer the same quality and price as didlogic.com, but with a convenient app interface, that would be awesome.