Samsung Galaxy S2

Android 4.0.3


Issue: Every time after I hang up from a call my phone will switch to vibration/ Silent mode!

As one would guess this is driving me mad, at first I was thinking.. its bumping to silent when I put the phone down or in my pocket! So lock screen, not working.

I have been hitting up Google over it and can’t find anything.  

Please help or I may just go mad! By the way I’m a heavy phone user 3 hours per day call time.
Phone is 1.5 years old and is a Vodafone handset.