I've seen this before, but can't find it now. Where is it at on the site?
If you go to "Manage Features", it would be listed there.
I just got mine working (at least for outgoing messages - not sure about incoming yet). I called and had them remove the MMS Opt-out and I did the reset network settings, outgoing call, etc. The girl did say that my plan was not compatible with the iphone because it's old (I've been told that before though). She removed the opt-out and put a pay per use option on there; however, once I got my first MMS to send, she said that I shouldn't be charged because I have unlimited data and a text messaging plan. I told her to just leave everything alone for now and I'll monitor it to see if I'm being charged 30 cents per message. Plus I still need to confirm that incoming MMS works properly. I'll post back with any new info.