HT1430 How turn off data when am not in WiFi location noticed am using data when phone on and am not in WiFi situation but not on internet. So how turn off data

How can I turn off the LTE data when I am someplace where there is not WiFi and I do not want my LTE running up a bill? I have tracked my usage and realize that the LTE is being used even when I am not using it, just because the phone is turned on.