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

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.