iphone 6s only 4G tab no LTE

You need to go into Settings, Cellular, Cellular Data Options and make sure Enable LTE is not set to Off. If it is, select Voice & Data (or Data Only) then see if your 4G indicator switches to LTE.

To force it to reconnect to the cell tower, you can always temporarily switch it into Airplane Mode then turn that off.

As far as I know, 4G and LTE and different names of the same thing.

Source: https://en.wikipedia.org/wiki/LTE_(telecommunication)

Try contacting your carrier.

Quote from Vodafone.de's website:

"Basically, LTE and 4G are different names for the same thing. On some phones you’ll see an ‘LTE’ symbol and on others a ‘4G’."

The difference should be normal and due to the different iPhone model.

If you can't make or receive calls on your iPhone - Apple Support

noted as "Tap Settings > Cellular and turn off Enable LTE, 4G, or 3G (this option will depend on your carrier and device model)." in Check your network settings section.

I guess (not sure), Settings menu says

4G : LTE with optional VoLTE ( supported on iPhone 6 or later )

LTE: LTE for data only ( iPhone 5/5s/5c )

3G: no LTE

For the status display ( top on screen ), the use of LTE or 4G is choice of the career ( part of career setting data ).

In my case, it was shown as LTE before, but it is changed to 4G when career setting data is updated.

you don't have to worry about the terminology "4G / LTE"

i did a test with a friend once, he has an andoid device, LTE connection 85 mbps in ookla speed test.

i've inserted his sim tray in my iphone 6s, 4G connection, no LTE but speed is the same...85 mpbs.

so if you don't have an LTE option on the iphone, it means that the carrier doesn't offer that for the iphone.

you may however go to "settings, general, about" maybe an update of the carrier pop-up message will appear.

it is just a word for me anyway, i've seen some LTE speeds in the U.S with 8 mpbs...

I got 6s plus 2017 and actually i have LTE