Why do I have a mini toggle on/off switch under my internet symbol?

That appears for a short amount of time after you first activate an iPhone X series or higher. That is to show you where to swipe downwards on the screen to access Control Center. After you have done that, it should disappear. It is sort of a help icon to help you understand the use of the iPhone.

It would be better if you can please post a screenshot, in order to understand the phenomenon better.