I've had this problem as well and didn't realize that it was due to my Bluetooth headphones till this past week. It's been driving me nuts! And it doesn't always change the ringer volume. Maybe it depends on how you connect/disconnect the headphones. As far as I know, there's three ways of disconnecting headphones 1) Turn off headphones 2) Turn off Bluetooth 3) Go into airplane mode. Two ways of connecting (after first pairing) 1) auto connect when Bluetooth is active before powering up the headphones 2) Turn on headphones, turn on Bluetooth on iPhone, press button on headphones to connect. I'll do some experimenting with different off/on techniques to see if one of them causes the problem. Or maybe it's the headphones themselves that cause this problem. I'm using Bluebuds X