Ringtone=/=text tone?

I recently purchased a ring tone from the store and tried to set it as a text tone. The ringtone itself is under 30 seconds and is very short. I went through the notification Center and set it as the default notification sound for messages. I'm having trouble because whenever I revive a text the default sound plays, not the tone I purchased and set it as. I double checked everything and it should work, but I still get the default tone. I don't know where I went wrong, help would be very appreciated. The only thing I can think of that might prevent it from working is that I haven't updated my operating system