If you need to change your service provider, or your SIM card is faulty and needs replacing on iPad Wi-Fi + 3G, you need to remove the micro-SIM card.
To do this, follow these 3 easy steps:
1. First insert the end of the SIM eject tool into the hole on the SIM tray.
2. Press firmly and push the tool straight in until the tray pops out.
3. Pull out the SIM tray and remove the micro-SIM card from the tray.