This Life Hack Will Save You From Great Troubles

If you want to switch off your mobile to avoid the unwanted calls or some for other reasons:

Then don't switch off instead remove the battery from your mobile directly without switching it off.

How this will be useful?

Well the logic here is:

When you switch off, your mobile sends a signal to the Mobile Switching centre( a server in mobile operator's office which connects your call to the other number) and then it gets switched off. MSC (Mobile switching centre) updates your mobile number status as switched off. When somebody calls you, MSC looks up your status(which is swtiched off) and plays the announcment that Number is switched off.

If you Directly remove your battery without switching it off, then your mobile cannot send any signal to MSC that it is going to switch off as mobile's power instantly becomes zero. And now if somebody calls you MSC as usual searches you in its network area and as your mobile is not powered on to reply the MSC's search request, now MSC plays the announcment Number is not reachable.
Instead of number is switched off.

So You wont get the questions like " Why your mobile was switched off yesterday" as they will understand that you were in some no signal region :-) :P