Wifi turning of, Background data on LTE

Since the new OS, every time I turn on the screen I have to wait for the WIFI to reconnect, it shows LTE on, after a few seconds later it reconnects. Therefore ALL background data is running in the LTE, eating away my data while I am at home with WIFI.

What is going on? Why is this going on? If I turn my WIFE ON I want it to STAY on, even in stand by (phone screen off)

How can I get rid of this "feature"?

Thanks