I suspect fraud, someone might have placed something on my phone without my consent. I need support

It’s possible. You need to restore the phone to factory settings→Restore your iPhone, iPad, or iPod to factory settings - Apple Support, then restore a backup made before the incident occurred. Also, note that if they did get into your phone it’s possible they have all of the content of the phone, including any passwords that are stored on it, credit cards, health data, etc.

Did you give them your Apple ID and password? If so change the password immediately, and add 2 factor authentication if you don’t have it already.

• Change your Apple ID password - Apple Support
• Two-factor authentication for Apple ID - Apple Support

It would be very difficult to do anything out of the ordinary without jailbreaking your phone. If you are concerned, you can restore your phone as new and reload your most recent backup from before this incident.

Most likely no. Unless someone had possession of your phone for several hours there is nothing on it. What makes you think that there might be a problem?