mastersm, anything other then stock does not work with that code, I had a walkthrough on how to workaround that with sprint, it applies for any carrier, however it seems to be missing (deleted? dunno why it would be though). So, anyways, that number is your MSL, enter ##778#, click on Edit, enter that number in, then click on the menu, go to NAM Settings, first line you want to edit is Mobile Directory Number, this is your phone number, which I would hope you know, after that is the MSID, this you will need from your carrier.
The work around is pretty simple, do what I said, then call your customer service, tell them you need to program it, when they say enter that code in, type in ##778# instead, click Edit, enter your MSL, go to NAM Settings, then enter whatever info they say. Tell them their code worked, NOT that you went with another menu, they'll refuse to program it any further. Or, sprint did, twice. All you really need is the MSID, so you can just do what I said, set your MDN, (that mobile dir number/your number) then call the rep and just wait for them to tell you what to do, play along like you are doing it, then once you get to MSID enter it in the line, hit OK, reset, welcome to service.
This assumes the ESN is registered as the current phone, of course.
Edit, found my workaround post, it didn't show up before for some reason. Normal search wouldn't find it.
http://forum.ppcgeeks.com/showthread.php?t=83799