Called AT&T @ 3:30pm EST. Told the rep that I had put my Sim in a different phone and couldn't find how to change my plan online. This is a great thing to say as the rep (at least this one) didn't mention anything about a micro-sim being incompatible with a dumbphone.
She asked for the IMEI number which I gave to her (after fake typing in the code that she gave me) and asked which plan I wanted. I asked for the $30 messaging/data plan and she said it wasn't available. I said I saw it online and after a very brief hold, she said it was added and I thanked her and hung up.
Checked OLAM and I verified that I have the $30 unlimited messaging/data plan. Now just waiting for the 1st round of texts.
Rebooted the phone, made a few calls to. Phone is showing as the iPhone 4 in OLAM. I also cannot use data (getting the "cannot activate cellular network" error). I am aware of the fix for this but want to see how it plays out in the next few hours.
Step 1 is done...hopefully this works!!!
Just to update..i got the two text messages literally 2 hours after i completed the above call. Logged into OLAM and it is now showing $30 unlimited...woooohooooooooo. Thank you so much OP and whoever else got credit for this...so awesome no worreies anymore.
I also just came back from the AT*T store and picked my brother up a 32gb iphone 4..switched to a family plan now have to do this again so he can have unlimited data also..