I have updated my iphone software to 6.1 on my 3GS and now my cellular data network is not available. Can this be fixed or can I restore an earlier version again?
I contacted my carrier (o2) and issue was resolved easily. It appears that Data Bolt-On, that I subscribe to, was no longer iPhone compatible. I was advised that this setting was affected by the Software Update. Not sure I really understand how or why but I was assured that the setting had now been amended and data services would be restored at midnight tonight
Did you check your settings for your APN? Since iOS 6 it tends to clear the value on random times for some people. You can check this within Settings > General > Cellular > Cellular Data Network > APN.
You can only edit this setting if your carrier allows this. More info here: http://support.apple.com/kb/ht2283