Lost Phone

See the information in https://support.apple.com/en-us/HT210515#erasedevice

and be sure to note the following from that link:

To prevent anyone else from accessing the data on your missing device, you can erase it remotely. When you erase your device, all of your information (including credit, debit, or prepaid cards for Apple Pay) is deleted from the device, and you won't be able to track it using Find My.

Also see: If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support