bitsy16 wrote:
How do I remove someone else (who is synced to my Apple ID illegally
Not possible for anyone to be "synced" to an Apple ID. If they are logged in to your Apple ID on their device, then that's just what they did. You can change your Apple ID password to stop them from being logged in.
- long story; involves misuse of a waiver and synced, cloned devices) from using my hotspot on my iPhone and running up my data usage???
Not sure what that means exactly.
All I see is a spinner on the cell data side of things. Sorry. I'm not technically savvy in all of this. I generally use my phone as a phone and not much else.
The spinner would just show up if your device is using data, not if another device is using data through your personal hotspot.
When a device is connected to your personal hotspot, a green pill shape with a chain link icon will appear over the clock at the top left corner of the iPhone for a moment when they first connect. The chain link icon will go away and the time will come back, but the green pill shape will remain around the clock while a device is connected.

click here ➜ Status icons and symbols on your iPhone - Apple Support
If that is not there, then nobody is using your Personal Hotspot.
Why do you believe someone else is using your personal hotspot? They would need to be within a few feet of you to be able to do this. Like in the same room for instance.
You can go to Settings ➜ Personal Hotspot ➜ Allow others to connect and switch that off to prevent anyone from connecting.