How do I check if my iPhone has been compromised by hackers?

Your phone has not been compromised by hackers; for all practical purposes iPhones cannot be hacked remotely. What personal protection was exposed to fraud? About the only thing that can be compromised in an Apple environment is your Apple ID, and, if you have 2 factor authentication for your Apple ID even that is unlikely, as you would know if someone tried to log in with your correct Apple ID and password, because you would get a request for a 2 factor authentication code that you didn’t expect.