GT-i9300 stock firmware download

You can't download wifi.

It depends on many factors e.g. country/carrier etc. The best way is to contact Samsung and request a factory unlock code (not cheap though)

there are a few reasons that it may not be ringing. First is that the notifications volume and ringer volume have been set to have different volumes. You can check this by tapping on the apps button (default is lower-right on home screen) then go to settings, and depending on your version of firmware installed, (i have sprint galaxy S3 SPH-L710 running stock KitKat 4.4.2 and will attempt to post screenshots for guidance) there may be tabs on top labelled "Connections," "My Device," "Accounts," and "More." If you don't have these tabs then you should be able to see the Sound option. First check if the volume is turned up. Go to Sound and then Volume and check to see that the sliders are towards the right (my phone is on silent due to not wanting to disturb anyone as it's night time.) If they are, then press OK and check the ringtone is not set to a quiet ringtone or silent. Have someone place a test call

Before buying anything, back up your S3 data using Samsung Kies. Then do a factory reset.. followed by a data restore..
firmware updates can cause problems until the handset is reset, as parts of the previous firmware are still in use..
You should notice an improvement after this... mine went from half a day, to almost 2 days usage, just by doing this after a firmware update.

You have managed to corrupt your EFS folder where your IMEI is stored.
Usual reason is that you have installed a non network firmware on a network locked phone.
Reinstall the network firmware to resolve IMEI NULL issue.

Once the issue is resolved, Get the IMEI number by typing *#06# on your mobile phone and get the IMEI number. Then visit
OnlineGSMunlock.Com to get the unlock code for your Samsung Galaxy S2 at affordable cost. with easy unlocking guide. Good luck.

Download Samsung Kies can do every thing in that

You may download a copy of the manual at http://downloadcenter.samsung.com/content/UM/201207/20120706131108550/VZW_SCH-i535_English_User_Manual_LG1_F5.pdf

Hi, if the phone is asking for SIM Network Unlock PIN or Enter Network Lock Control Key, it's possible to unlock it by USB or network codes on fastgsm.com

you have to update the firmware or downgrade it depending which one is giving you problems. i had the same problem with mine. i upgrade os and facebook ran smooth
hope it helps