[Mega-Japan]

Does anyone have a problem about the ringtone, any ringtone, playing in very low volume when receiving a call?
the phone's volume is on max, and when I play songs regularly, the play in the volume they should, and when I test the ringtones, they also play at high volume. But when I actually get called, it's like the volume is halved.
Anyone knows why? And is there any fix? Thx.