Lost Iphone

From my understanding, Your iPhone has been lost or stolen and someone has turned off find my without your permission.

So Sorry to hear this happened to you!

I would start with https://support.apple.com/en-us/HT201472 "If your iPhone, iPad, or iPod touch is lost or stolen"

Step 1 goes over how you can also go to iCloud.com/find to try and locate the device.

If you the device is not showing and you believe that it was turned off without your permission, then I would definitely contact Apple Support

If the device is showing as OFFLINE : Currently, the device is not connected to either a cellular or WiFi network, hence the "offline status". Put the device in lost mode, have it display a callback number for the person who finds the phone to call.

Contact Apple > https://support.apple.com/en-us/HT201232

Hope this helps ;)

Please do not call or text that number above. That is not an Apple phone number.