How do I unlock my galaxy s3 att from its PUK code 8 numbers?

SOURCE: PUK Code after entering pin incorrect x 3

The PUK code MUST COME FROM THE SERVICE PROVIDER as it is SIM specific! I would ask to speak to a supervisor if after identifying yourself as the legal owner of the SIM they refuse to give it to you!
Most service provider will also give you the PUK code in your Pre-Paid Online management site when you register the SIM online.
Hope it helps!

SOURCE: how to brighten the screen during internet usage with galaxy s3

While in browser, open settings (bottom left button) and change display setting. The s3 has separate display settings for browser and general phone. Hope this helps.

SOURCE: sim network unlock pin for samsung galaxy s3

You can unlock it by codes (by IMEI officia unlock codes) or you can unlock it by cable. Both are available from http://www.unlocksamsungonline.com/unlocksamsung/I9300

This website is a trustable resource and in operation since 2006.

SOURCE: samsung galaxy s3 GPRS settings

Scroll your finger down from the top of screen, will bring down notifications menu and should be wifi and that there at the top. Or its under settings in the menu.

SOURCE: How do I set voicemail ringtone for Samsumg Galaxy S3

Click on phone icon, click menu > call settings > scroll down to voicemail settings select ringtone select the ringtone you want click OK