Q: if find my iphone is off on the phone will i ever be able to disbable the lost phone?

This should explain what happens:

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

Note the section:

What if your iOS device is off or offline?

If your missing device is off or offline, you can still put it in Lost Mode, lock it, or remotely erase it. The next time your device is online, these actions will take effect. If you remove the device from your account while it's offline, any pending actions for the device will be cancelled.

Sorry to hear you lost your iPhone. Unfortunately, the only way for it to communicate with the iCloud servers to erase it is to have Find My iPhone turned on and the device connected to either a cellular network or previously known wifi network.