When turning off my iPhone the circle spins and the phone does not turn off

Not sure which iPhone you have but-

1. Force Close All Your Apps as shown in this article by Apple ➔ How to Force Close Your Apps.
2. Force ReStart Your iPhone as shown in this article by Apple ➔ How to Force ReStart Your iPhone.
3. Once the first two steps are completed. Then try and turn off your iPhone like you normally do.

Hope that helps.

Axel F.