Mine does too, I think it may have to do with the firmware that the carrier can send (like with other phones) or has to do with GSM identity code, and may be different when roaming, so it will show you when you are on a CinciBell or AllTell.
2.6 is not listed. oh well, just another mystery I guess. I thought perhaps it may have something to do with your signal tier, and a certain carrier package would have better service.