A 3G SIM card offers the fastest mobile service for cell phone users. Most newer cell phones offer 3G service with their cell phone plans. You won't be able to tell if you have a 3G SIM card just by using your cell phone. In order to tell if you have a 3G SIM card, just look at your SIM card. 3G has a symbol on its SIM cards that lets you know that it has 3G.
Shut off your cell phone. Just hold the "hang up" button until the phone powers down.
Remove the back cover of your cell phone and take the battery out. Underneath your battery will be the SIM card.
Remove the SIM card from your phone. You will either be able to slide the SIM card out of your phone or you will have to unhook it from its place.
Look around on the SIM card for a 3G symbol. If the SIM card is 3G, it will be written on the card. If your SIM card doesn't have a 3G symbol on it, then it is a 2G SIM card.
Put your SIM card back in your phone, replace the battery and put the cover back onto your phone.