Q: I have an iPhone 6s the to/cc line just appeared with my email accounts. I go to settings and toggle the switch and it won't go away

Greetings PossumAsks,

From your post I gathered that in your inbox in the Mail app, it is now showing the Show To/CC Labels even though you have toggled the switch off. I use email as well and I know it's nice to have the inbox showing without the extra information. I will be happy to help you with this.

The first thing that I would recommend you doing is to force close the Mail app on the iPhone, and then restart the iPhone. 

Force an app to close on your iPhone, iPad, or iPod touch

Restart your iPhone, iPad, or iPod touch

Then once back up on the Home screen, please go ahead and relaunch the Mail app and check to make sure the inbox is loading as expected.

Cheers!