I'm still familiarizing myself with the Casio Commando C811. Under Settings > Sounds I've set the default notification and the phoneringtone. While at home the cell phone is normally connected to the Internet via WiFi as the towers are too far away and blocked by hills. I sometimes receive text messages via the Internet and e-mails, both with a ringtone and a visual notification. I don't normally have any problems picking up phone messages, text messages or e-mails. However every once in a while I here the default ringtone when I haven't received any phone, text or e-mail messages. I'm uncertain which app is producing the ringtone as I'm not able to find a visual notification.