When it comes to determining WHETHER a Sim is Faulty, Here's Tips:
IF you have Multiple Devices, AS LONG as It's UNLOCKED, Compatible, insert Sim
IF There's NO Signal, like NO Public Mobile being listed on top screen on Device, Possible Dud, As you wouldn't be able to Call In/Out, Receive or send out Texts, or Data
IF You have Text In/Out, or Talk In/Out, Doesn't mean Sim Dud, could be that Network issue and just talkking to Moderator can resolve issue
