For the iPhone 6S, is there a way to stop its tilting from being so sensitive?

I recently upgraded to an iPhone 6 when my old iPhone 4 went belly-up. When you tilt the phone, everything on the screen reads horizontal instead of vertical. This would be fine, except it is So blankety-blank SENSITIVE! It seems to want to tilt horizontal at the slightest movement, and one its tilted, I have a devil of a time trying to get it go vertical again. I prefer a vertical display, especially when I'm texting; it's just easier for me to read. To get it back to vertical, I have to try shaking it slightly and then turning it all the way around, sometimes a 180, sometimes a full 360. And half the time when I do that, a slight jiggle and it's horizontal again! Grrrrrrrr…

I can't seem to find anything in the settings about changing this sensitivity, but maybe I'm not looking in the right place or just missing it. Can anyone help with this?

There should be a setting you can turn off about screen rotation that you can change to remain in the one view only.