Facebook is often the best place to find people sharing rumors and falsehoods but one recent one about huge phone bills from data overages and wifi assist was in-fact true.
Apple makes it sound like a great new feature, and it might be if you have horrible wifi and unlimited data. The key here is unlimited data. If you do not have unlimited data and normally watched Netflix or other services on your phone or tablet, that use massive amounts of data, your wifi assist could be using your wifi and your data services via Verizon, etc. without you knowing it. Even worse, it’s turned on by default.
If you read Apple’s support documents you’d think this was a great feature, and again, by all accounts its a really good thing for an educated consumer who might decide to turn it on (not get a massive phone bill and then pay the price for this unknown feature).
If you do not have unlimited data you should turn this feature off. It’s pretty easy:
Go to Settings > Cellular. Then scroll down and tap the slider for Wi-Fi Assist.