You can't the ISP already know all the hacks and will have prevented you. They know the so called unlimited plans on cell phones is a lie......almost nobody watches hours of netflixs at 4k on a tiny screen.
The phone itself know when it is running in tethered mode or hotspot mode. In some cases if even data you use from the phone itself when you have hotspot active will get counted as hotspot. The phone is telling the ISP even if your run VPN.
You are going to likely have to root the phone to bypass stuff like this. Not going to get details on how to do that on this forum they will lock and delete the posts.