If you place or receive a phone call and the other user cannot hear what you are saying, it is possible that your microphone is deactivated. This happens when you didn't give the proper authorization to Instantgo to activate your microphone while using the app.
To correct this problem, you need to go to the Settings of your phone:
From that screen, you need to scroll down to the bottom of your settings where you can find all the different apps you have installed. Click on "Instantgo" when you see it.
You will then access this sub-menu where you need to activate the microphone option. This will let other users hear you when you place a call using Instantgo.