This problem was resolved with this piece of code:
public void call(String dialNumber) {
try{
Intent callIntent = new Intent("android.intent.action.CALL_PRIVILEGED");
callIntent.setData(Uri.parse("tel:" + dialNumber));
startActivity(callIntent);
}
catch (Exception e) {
Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:" + dialNumber));
startActivity(callIntent);
}
}
where this was crucial: "android.intent.action.CALL_PRIVILEGED"
After applying this, new window was opened offering for call to be made by all possible means for placing call - in this particular case, they were Dialer and Viber and Skype (or any other method added later).