Android : Pop Up Screen Whenever Received Message

I kept getting this pop up screen whenever I received message. The pop up screen is so big that my message will be displayed and anyone can read it. I have searched everywhere on the setting to turn this off, I also called the support and they cannot help me. The pop up screen has the sender phone number, the message, a sunglass and hello message. At the bottom, it has reply, dismiss or replay with a busy message. I am using nexus 1. It is very irritating to just keep getting the poop up without any privacy.