My SIM card is not working properly? My phones will not detect it?

I have a t mobile dash 3g by htc and it is saying the SIM card cannot be detected. I tried putting my SIM in a different phone and it said the same thing. It just gave up the ghost? I tried taking an eraser to the SIM card as that is used as a fix for many people but it did not work for me. How can this be fixed?