My iPhone keeps using cellular data even with Wi-Fi Assist and LTE turned off?

My iPhone is an iPhone 6 and my service is Verizon. I have a 10 GB limit for cellular data between me and my brother that our parents set up when we both got our phones.

I have my iPhone set up to only use Wi-Fi in my home and use cellular data when I'm outside my home away from my routers Wi-Fi signal.

But a few days ago all of a sudden it started using up data even though I was in the house and had Wi-Fi Assist off and LTE turned off instead of "Voice and Data" or "Voice".

Before with my usual set up my used data would not go up while in my home because it was connected to the Wi-Fi and went up if I used data related stuff outside it.

Now its going up both at home and outside.

How do I get this to stop and get my phone working to how it was before?

Turning LTE off just means that it won't connect via an LTE mobile connection - it'll still use mobile data, just not LTE! So if you've turned off the phones ability to use Wi-Fi it will default to using (none-LTE) data! If you don't want it to mobile data you have to turn off the mobile data totally and not just stop it from using fast(er) LTE!