Samsung Galaxy SIII APN problems

[Anonymous]

I recently updated my Samsung Galaxy SIII (i9300) to a newer version of android. After I had updated I noticed I cannot use 3G, SMS messaging or calls. I presume there is something wrong with the apn I'm assigned to so I searched up the correct o2 pay monthly apn, I found that the correct one is mabile.02.co.uk so I went to check that I was using that one but when I opened the 'Access Point Names' menu I found that there were tow mobile.02.co.uk apn's (Neither of these seem to work) does anyone know how to fix this? Because at the moment I cant use my phone as a phone.

[Anonymous]

when i dial it it says 'mobile network not available'

[Anonymous]

also when trying to go into the settings for calling it says 'network or sim card error'

[MI5]

It's not looking good so far.
What root method did you use?

[Anonymous]

erm that was a long time ago i have CM6.0.4.3 bootloader ill find the video i followed 

[MI5]

Yes, that was a long time ago - Any particular reason that you need root?

[Anonymous]

a fair while ago i used cyanogen mod but i have since returened to stock because of one of the updates for cyanogen drained battery excessivly

[MI5]

OK, so you happy now to get rid of root and flash latest stock ROM again?

[Anonymous]

Yeah ive got the latest stock rom but its still rooted shall i unroot it?

[MI5 · Accepted solution]

Flash MK6 with Odin.
It will remove root anyway and is the safest method of restoring your phone to stock.
Download MK6 from here http://www.sammobile.com/firmwares/ (type i9300oxa in the search box and MK6 is top of the list).
Then follow the Odin flash guide I wrote here http://community.o2.co.uk/t5/Android-Devices-Samsung-HTC-Sony/HOW-TO-A-Guide-to-using-Odin/m-p/46346...

[Anonymous]

Thanks ill try that and get back to you