Lost my Nokia Mobile How to Block It from Others to use

Hi arun! You should immediately request your service provider to deactivite your SIM card so that others could not use it. As far as your personal data e.g. contacts and SMS/photographs etc. in the mobile handset is concerned, nothing could be done much about that. You always need to keep a back up data of your mobile.

Contact the nokia service center and give them the IMEI number.

First call your provider and make sure those who've found it cannot call. If your mobile was off during you losing it, mostly they won't try to break in, because it would mean they'd have to find a fitting charger and mess with your code. Let's hope your code was not 0000, or 1111, or 1234 :(

I know this is a little late, but the best advice to offer if you've replaced the phone, is to password protect it from being used. Don't use the provider's defult change it to some unique code only you know. That will protect your files photos and what not. Though you should also back up your files etc on your computer if you can in the event something happens. I have to do that regularly I've already lost a good phone or two. So I know how it feels.