If you hear 2 text tones when receiving a text, disable your system text notification sound and enable a default text tone in the preferences for the app. If you have another app that is playing a tone when you receive a text, you will need to disable that functionality in that app.
If your phone doesn't allow you to set a ringtone to "Silent", please download:http://software.roadkill.com/CustomSMS/silent/Silent.mp3 and use that. It is a 1 second silent MP3.
Please email email@example.com if you have comments/questions/problems with the app. Leaving comments and ratings in the market is great, but we have no way of contacting you to respond to your comment.