Hints to fix the Samsung Galaxy S that do not detect or recognize SIM card:
1. Try to use another known good sim card.
2. Visually check the SIM card holder for possible damaged, clean it, re-solder and fix if the pins were misaligned. Replace the whole SIM card PCB board assembly if necessary.
3. Check/clean the SIM card PCB assembly pin connector.
4. Check the VSIM supply voltage. You can read around 1.8V -3V when the sim card is inserted.
5. Trace each of the VSIM, SIM_RESET, SIM_CLK, SIM_IO and GROUND pins connections down to the pin connector.