Mobile data being used while on wifi?

[HBKSeanMichael]

I have a Galaxy Note 10+ and I was at home today and out of no where I got an alert saying that I had just exceeded my monthly data limit and was now in data saver mode. Both devices on my plan were at home all day...

What could have caused this? I know in the past I have seen a setting that will improve your download/upload speeds by using mobile data and wifi together but I can't find that setting anywhere to check and see if it is on.
Besides that, I am clueless how this could happen and seems pretty shady on Verizon's part...

 

[adegbenroagoro]

The description is slightly different than in the past. Connections~Wi-fi~ Advanced~Use mobile data with wi-fi. Switch it off.