As long as the SIM was never activated on a different number, you're fine. But say, like me, you got an additional line to buy a new charge, tb, whatever, then flipped it to your primary line to be your primary phone, and then discovered the tb sucked, or sold it or whatever, YOU WILL HAVE TO REPLACE THE SIM. It will not work if used on a number other than the one you are activating it for... I don't know if this is your issue, but just fyi
