Iphone will connect to Wi-Fi but not 3g/4g/mobile carrier?

I got my iphone 5 wet and it will connect to Wi-Fi but will NOT connect to my mobile carrier. This makes me believe that i have something bad with the sim card/sim card reader. What do you guys think?

Settings-General-Reset-Reset Netwoerk Settings. You will have to rejoin wi-fi. It that doesn't work take the SIM out and put it back in. If that doesn't work contact your carrier.