Lumia 1020 :: Internet Sharing Completely Gone After Cyan Update

I'm using an unlocked ATT 1020 on Tmobile and when I enabled internet sharing, it would tell me to call 611 and request the feature from ATT. But if I disabled LTE, tethering would work and then I could re-enable it. Now, with cyan, the phone recognizes that it's going through tmobile, but states that I don't have the mobile hotspot service (I do have it) and takes me to a message to upgrade my plan. When I click upgrade, it takes me to a page to call Tmobile. Upon calling them, after dealing with someone who swore my plan didn't include tethering (it certainly does), I got transferred to someone else.

After some steps and some research on their side, I was told that the only thing that made sense was that when I changed my plan to a higher data plan (recently, where I was assured nothing would change except the amount of data), the system saw that my phone was not a Tmobile one and kicked tethering off. She stated that there was no way to manually re-add it because it just kicks it off again. For the record, all of the other phones on my plan still work with tethering (one other phone is a non-tmobile iphone). Also, a friend of mine has a 1520.3 on the same plan and cyan actually made internet sharing work when it wasn't working before. So confused and frustrated.

I don't know if this was actually something cyan changed or if it really was the plan change, because I believe the last time I tried internet sharing was before both changes. I want to try my sim card in a pre-cyan, non-tmobile WP and see what happens.