On AT&T, will I be charged data if using 3g/4g, with an LTE plan?

I have a 30$ per month LTE plan on my iPhone 6, and noticed an option to turn off lte, restricting me to 4g or 3G. Is this still going to charge usage on my account?

Yes it will still use data and you will still be charged. If you want to save data you need to turn cellular data off. You can still use Wi-Fi for free though.