My s3 has froozen

From the Official Samsung website,
this is the Samsung Galaxy s3 PDF manual in English (for FREE, at no cost):

GT i9300 International Version
http://downloadcenter.samsung.com/content/UM/201302/20130228184012484/GT-I9300_UM_EU_Jellybean_Eng_Rev.1.1_130228_Screen.pdf

AT&T Version:
https://www.att.com/support_static_files/manuals/Samsung_Galaxy_S_III.pdf

Sprint Version:
http://support.sprint.com/global/pdf/user_guides/samsung/galaxy_s/samsung_galaxy_s_ug.pdf

T Mobile Version:
https://support.t-mobile.com/servlet/JiveServlet/previewBody/6302-102-2-21849/Samsung%20Galaxy%20S%20III%20User%20Manual.pdf

Verizon Version:
http://downloadcenter.samsung.com/content/UM/201207/20120706131108550/VZW_SCH-i535_English_User_Manual_LG1_F5.pdf

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Your Samsung Galaxy S3 must be restricted to some specific network. That is why it allows only emergency calls when a SIM card from some other network is inserted in. You need to unlock your Samsung Galaxy S3 to make it work with all SIM cards. You can unlock your Samsung Galaxy S3 safer and easier using unlock code. You can get the accurate unlock code for a Samsung Galaxy S3 from Unlock-Zone.com at affordable cost. Good luck.

-<()>--<()>--<()>--<()>--<()>--<()>--<()>-
..............UNLOCKING INSTRUCTIONS..............
-<()>--<()>--<()>--<()>--<()>--<()>--<()>-

Method 1:
1 - Switch ON your Samsung Galaxy S3 with a NOT ACCEPTED SIM Card.
2 - Samsung Galaxy S3 will ask for "Password".
3 - Enter the Unlock Code.

OR (if the Samsung Galaxy S3 shows "Insert Correct SIM Card")

Method 2:
1 - Switch ON your Samsung Galaxy S3 with a NOT ACCEPTED SIM Card.
2 - Don't bother about what's being displayed on your Samsung Galaxy S3.
3 - Compose : #0111*CODE#.

SOURCE: MobileUnlockGuide.com

Too many steps to write here. Do a Google search, "root g3" or related. Here's a link to get you started: http://gs3.wonderhowto.com/how-to/easiest-one-click-root-method-for-your-samsung-galaxy-s3-0155625/

Get the unlocking service from an online vendor like
http://www.wickedunlock.com/samsung-galaxy-s3/rs11wp9/ to unlock your Samsung Galaxy S3 from network lock.To get the service you need to submit your country name,currently locked network provider name and IMEI number.

call samsung toll free no
or go to samsung store/service centre
they'l upgrade it properly
sometime we are not good to handle it ie how to upgrade/restore

To use your AT&T Samsung Galaxy S3 with T-mobile network,you need to unlock it from current provider.Get the unlock code from the site Simpleunlocking.com and get free Unlocking instructions from the site Mobileunlockguide.com ,unlock it step by step easily.

You can Contact your network provider and request an unlock code
Insert your new SIM card
Power your Samsung phone on then enter Unlock code.
For more details you can check at Samsung India site.
Samsung Galaxy S3 Price India Buy 3 Smartphone Features Reviews Specs

Hi, You can unlock your Samsung Galaxy S3 safer and easier using unlock code. You can get the unlock code from http://www.wickedunlock.com/samsung-galaxy-s3/rs11wp9/ at affordable cost with easy unlocking instructions.