My friend came to me the other day with her S3 as it was unable to connect to her network (Tesco Mobile) there is no problem with the sim as it works fine in another phone.
I have tried all the settings and every solution I can find on Google, such as turning off all connections , turning on aeroplane mode, rebooting and then trying to connect again but still with no joy.
I have also flashed cwm to install Paul Obrian's Modaco S3 from (which is very nice by the way) but I am still having no joy.
Finally when I scan for networks Tesco is not on the list and get unable to connect. Try later when trying to select any network.
Thanks in advance