gearsmithy The settings that I'm trying to get you to look at are below the call preference and SMS preference that are grayed out. It sounds like you're getting to the correct setting screen, but you just need to scroll the page below the two grayed out options that you see. Directly below the SMS preference that's grayed out, you should see mobile data, then roaming, then app data usage, data warning limit and advanced calling. That's where the use LTE service toggle switch is. Then below that is preferred network. Make sure these are set to the "recommended" option.
Sorry, not trying to frustrate you or make you crazy. LOL. You're on the right page. You just need to scroll down past those two grayed out options to get to the other settings.