I've been on the phone nearly every day with Samsung and tmobile trying to figure this out --- no one seems to know anything -- so I am now drawing my own conclusion:
Since the phone came out 14 days ago, they haven't even shipped the accessories, such as replacement batteries or backings or anything - because this is still under the 'buyers remorse' period. After tomorrow, the buyers remorse period will be over and then they will be able to accept 'warranty' requests -- at which time, batteries and other accessories should start appearing.
Quote me all you want, but this is just my opinion and very well could be mistaken.
We'll find out soon, and in the mean time, like me, carry a charger with you everywhere, because this phone's battery life just melts away.