Smart Talk is a great app but during a call the screen goes blank, with a dimmed white/grey screen. You do see the options for accessing the Keypad, ending the call, etc only for a split second then the screen goes blank.
This means that during a call I therefore can't access the keypad, eg to respond to a menu option on a call, or even end the call (for which I have to force stop the app from my phone's settings!, or wait for the other person to end the call first).
Tried turning off screen proximity sensor on my phone - no difference
PS I'm using the latest version of the smart talk app on android (Samsung galaxy s4).
Same issue here exactly with my galaxy note 3 android 4.2.2.. it wasnt before, till registered a another mobile number on my second mobile.. tried to clear data and reinstall the app but no improvement.. dont know what is the link between registering new mobile number and the app screen goes off on my first mobile while making a call.. noticed also i have to make the call from the app itself.. which wasnt before also.. normaly was opening the phone dialer and when dialing 0845 nos for example the smarttalk app automaticaly detect the number and shows a msg advising to make the call through the smarttalk as cheaper rate.. once choose yet it launch the app automaticaly.. Any advice