Unfortunately I have the same issue as some of the other posters on this thread.
I'm using a T-Mobile SIM, and I'm in Southern California. Nokia Messaging is missing from the list of providers, which is unfortunate.
I also don't have access to another provider's SIM at this time. Not really a big deal, as I can still use IMAP to get my email, but I imagine I'll have to wait for an official 'fix' or so.