Yes, you can turn off LTE to use 3G or 2G networks on your phone. You can select the preferred network in place of LTE while turning it off.
For Android devices, follow this command route:
Settings > More > Mobile Network > Preferred Network Type > 3G or 2G
For iOS devices, follow this path:
Settings > Cellular > Cellular Data Options > Voice and Data > 3G or 2G