How to contact Apple support for fraud-related Activation Lock on iPhone?

You can try to get Apple to unlock it by providing the required information. However, in the case of a scam it is likely the scammer put it in Lost Mode and Apple very clearly states they will not unlock a device with Lost Mode set.

Apple needs the original sales receipt from Apple itself or an Apple approved vendor. Other ways you may think might be “proof” of ownership or purchase, such as having the box or a receipt from a third party vendor such as Ebay, will likely not be acceptable by Apple. Apple may have no way of verifying the authenticity of other methods. If you have an acceptable receipt, ask Apple to unlock the device —> https://al-support.apple.com/#/additional-support

Recycle the device if you cannot unlock it; it is now useless to you. From the very bottom of Apple Trade In - Apple :

"Does Apple offer recycling?

Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."

When considering future purchases, browse this: https://discussions.apple.com/docs/DOC-250001038

You can contact Apple directly here. Support varies by region, but most have the ability to talk to a live agent.

Contact Apple Support - Apple Support

If the device has been placed in Lost Mode, it is likely there is nothing Apple can do. Unfortunately there are actions on your part that can have serious consequences, and entering someone else's Apple Account into your phone is one of them.

• Another is if you give someone your Apple Account password, where they would then have the ability to delete your account entirely and data loss.
• Sending Apple Cash to someone you do not know could result in the loss of your money without any means to get it back.
• Giving someone the code to a Gift Card, whether it is a scammer or not, will result in loss of the Gift Card.
• Do not buy a used device from a third party where you have no option to return it. Some sellers are looking to sell stolen devices that will not work for the buyer and once sold will disappear.

We can tell you not to do that, but we cannot stop someone from doing that. Sometimes these are just hard lessons to learn in not believing everything you see on the internet. It is the Wild West of scams and not for those that are easily manipulated. Social Media is the source of many of these scams, so be cautious, many are not actually your friends and are looking to take advantage of you.