No LTE

• Where are you located (what country)?
• Do you have an LTE SIM?
• Is LTE enabled in Settings/Cellular (aka Settings/Mobile in some languages)?
• Have you applied potential carrier updates -->Update your carrier settings on your iPhone or iPad - Apple Support?
• What are the results when you run a speed test (speedtest.net app or go to http://speedof.me in Safari)?

Check in settings (Mobil Data - Mobil Data Options) if the LTE is enabled.

Those are LTE speeds, so even if it says 3G you have an LTE connection.

But you didn't answer if you applied carrier setting updates. This has nothing to do with the version of iOS you have; carrier data updates have nothing to do with the version of iOS.

Ask your carrier.

Where did you buy your iPhone?

~Lyssa