I sell some boost and nextel phones even though they are the same technology ONLY SOME NEXTEL PHONES CAN BE USED FOR BOOST AND ONLY SOME BOOST PHONES CAN BE USED FOR NEXTEL EVEN IF YOU HAVE ENTERED THE "SPECIAL CODE" AS IT IS CALLED IN iDEN PHONES IF YOU HAPPEN TO TRY TO USE BOOST SIM IN THE WRONG NEXTEL PHONE MODEL IT CAN POSSIBLY FRY THE SIM CARD AND PHONE  THE PHONES WHICH CAN BE USED FOR EITHER ARE EXAMPLES LIKE BOOST I875 NEXTEL I870 WHICH ARE ACTUALLY THE SAME JUST DIFFERENT COLORS AND I875 HAS THE WORD BOOST ON IT AND I87 HAS NEXTEL LOGO ON IT MOST MODELS THAT BOTH BOOST AND NEXTEL HAS CAN BE INTERCHANGED I835 IS BOOSTS EQUIVALENT TO NEXTEL I830 SERIES