I am using samsung galaxy S2
when i call for somebudy more times i always have to increase volume by side button were mostly i found very less..after analysing this problem second time when i found the same volume atomaticaly been less i gone to setting-sound-volumes all where max of volume
i dont understand this problem where in setting volume is max and when i call the volume is droped atomaticaly

please advice to fix this problem to fix max the volume on call