I've got SIP working with a number of different providers to the extent that I can call a number and the phone rings. But I get no sound at all from my headphones when someone picks up the phone I am calling. (Obviously they can't hear me as I have no mic, but I should be able to hear them.) I've put the volume up to full on my Touch, and tried restarting the Touch with the earphones plugged in and then starting the SIP app, but no luck. Any ideas?