Read the document Use Lost Mode in Find Devices on iCloud.com - Apple Support
When you find your lost device, do either of the following to turn off Lost Mode:
- You can turn off Lost Mode by entering your passcode on the device.
- In Find Devices on iCloud.com, click All Devices, then select the device that’s in Lost Mode.
If you still have questions or problems:
Refer to this document for ways to contact Apple --> Choose your country or region - Official Apple Support
Select your country (also look for "other" regions), then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service by telephone --> Contact Apple for support and service - Apple Support