I would try one of those bundles, or reset network settings and add the sinfuliphone repo and use their MMS/Tethering bundle. It worked for me when nothing else would (unlockit/custom carrier packages) I didn't use the spookyET thing because it blocks off the celluar data network option in the network settings area.
Let me start by saying Girl with too many L's is wrong about SpookyET's carrier bundle blocking network options. It used to, but he fixed it due to complaints from multiple people. I recommend his bundles, they work 100 percent for me. You can find them on the first page of the thread titled something like Tmobile USA Carrier Bundles (something like that, its on the first page of forum listings). You'll have to follow the instructions and pick the bundle appropriate for your plan. Also, make sure you turn mms messaging on in your message settings. Do those things and you should be good to go. Oh...and respring after uploading the bundle...if it still doesn't work reset your network settings and you should be good.