Below are some sure ways to check if you are looking for “how do i find out if someone is remotely accessing my phone?”
1. You can go to your Apple ID account and then check for the devices that are signed-in.
2. You can also check the security details on your Apple ID by going to the Settings > Sign in to Your ID > Select Review Your ID Details > Check all of your Details.
3. You can also check recent activity of the phone by opening Settings > Select General > Click on Usage > Select Battery Usage.