HELLO MY NAME IS SAL HERFY KNOW ON EBAY AS MR CHEAP CELLULAR. I HAVE BEEN IN THE CELLULAR BUSINESS SINCE 1997. IM ONE OF THE FEW PEOPLE THAT LIST HIS PERSONAL  CELL NUMBER 904-674-7575, LETS TALK ABOUT NEXTEL BLACKBERRY SIM CARDS, YES THEY ARE DIFFERENT FORM REGULAR NEXTEL SIM CARDS AND THERE ARE ONLY TWO TYPES OF SIM CARDS FOR THE NEXTEL BLACKBERRY THE FIRST IS A 32K BLACKBEERY SIM WHICH WORKS ON 3 MODELS 6510 7510 7520 THE SECOND BLACKBERRY SIM CARD IS 64K WHICH ONLY WORKS FOR THE 7100 MODEL. ANY ONE TELLS YOU ANY THING ELSE IS JUST A ROOKIE TO THE BUSINESS. ALL THE SIM CARDS THAT I SEE ARE FREE AND CLEAR WHICH MEANS YOU WILL NOT RUN INTO ANY PROBLEMS ACTIVATES OR SWITCHING YOUR SERVICE TO. SOME PEOPLE SELLING SIM CARDS DO NOT CHECK THEN AND WHEN YOU TRY TO ACTIVATE THEM IT WILL NOT WORK, BECAUSE THEY ARE MORE LIKLY TO BE ON SOMEONE ELSE ACCOUNT. HOPE THIS INFO HELPS