Place your Wistiki near your smarpthone.
If you press for a couple of seconds on your Wistiki's button, the smartphone should ring.
The more you turn up the volume of your smartphone, the louder it will ring.
Your smartphone doesn't ring when you press the Wistiki's button ? (Make sure your smartphone's volume isn't at 0)
Case 1 : if the "Ring" button is shaded in orange (when you press the "ring" button, the Wistiki rings), you have to close the app (go to the app center, then slide the app to the side) then open it again. This will fix the problem.
The app update, due January 2015 on the Store, fixes this problem.
Case 2 : if the "ring" button is grey (when you press the button, the Wistiki doesn't ring), the solution lies here