Why I cant force LTE?

I have a galaxy S5.

There is no option to put LTE Only.

I have android 6.0.1 Marshmallow.

Codes are not working. Internet unstable: switching between 3g and 3g+

Any hint? Thanks

from Android Forums at AndroidCentral.com - Ask a Question http://ift.tt/2fYkYPd
via IFTTT