I love that feature, my Stupid Motorola deletes the missed calls I get and I used to never know about them, but with this new feature I never miss a call
Go to the website, there is probably a four digit number you dial which will turn it off.
on orange you only get them when your phone was unavailable to the network at the time of the call.so either no signal or switched off,if your phone is always on you wont have got any.
handy feature for me as i go into no signal areas for short spells at work