Cannot access/change APN with iPhone 4.1 (Celluar Data Networking Missing)

Question

I updated my iPhone 3GS from 4.0 to 4.1 last night and this morning I notice when trying to retrieve mail I receive the error "You are not subscribed to a cellular data service" and I cannot access mail, the web or use any data related applications.
I do have the data plan and yesterday it was working fine. I confirmed with AT&T I do have the data plan.
I thought maybe my APN was deleted so I wanted to confirm it. But now when I access Settings->General->Network there is no "Cellular Data Networking" option and in fact it has been replaced with "Set Up Internet Tethering". I cannot access my APN settings.
I reset the network settings, rebooted and ejected/inserted the SIM card however this field/option does not return.
Questions:
1) With iOS 4.1, was the APN field moved?
2) Is there a reason it would disappear?
I confirmed I do have 4.1 and AT&T says my data plan is correct, active and did not change overnight. I simply want to confirm my APN says wap.cingular but the field is missing!
I am frustrated since all I can receive are calls and text messages but cannot retrieve mail or surf the internet.
My apologies if this is a known issue however I appreciate your direction.

Answer 1

Hi,
I'd like to suggest the following:
1. Perform a 'hard reboot' by pressing (and holding) the sleep/lock and home buttons simultaneously until your iphone reboots then check your settings after.
2. If that didn't work then try re-syncing with itunes (make sure you've got the latest version) and see if it pushes a 'carrier update' to your handset.
3. If the above procedures fail then you may have to redo the update process by performing a restore via itunes.
I actually do not have the option to edit the APN settings on my iPhone but this is because my carrier (Orange UK) restricts it by locking down the carrier settings file that gets pushed to all Orange UK iphones via iTunes.