i need to report phone lost

Did you pay for AppleCare+ Theft & Loss? That is an additional cost plan you would have had to purchase. And in order to file a claim, Find My MUST have been enabled on the phone before it went missing.

If both are true in your case, see this link --> iPhone Theft and Loss Claims - Official Apple Support

Did you purchase AppleCare+ with Theft and Loss coverage?

• Yes. Follow these directions. iPhone Theft and Loss Claims - Official Apple Support
• No. There is nothing to claim. AppleCare will not cover your loss.