If Cellular data is off, you will still see the carrier name, but 3G/4G/LTE icon will disappear. If cellular data is completely disabled, it will not use cellular data at all. The 23GB of cellular is probably the life of your phone and if you have used a backup going from iPhone to iPhone, that number never resets. I have an iPhone 4 with a backup that was on a 3GS and a 3G so it says my lifetime data is over 100GB, but its really probably closer to 30GB for that particular phone.