iPhone 7 Bluetooth not working

Ive been given an iPhone 7 to replace my old SE. Everything works as it should except for the bluetooth. When you go into settings, instead of the Bluetooth On/Off switch there’s just a spinning disc.

I’ve been through all the troubleshooters to the point of restoring it back to factory defaults with the latest IOS, but it still doesn’t work.

However I have noticed that when I put the serial number into Apples website, it should be a different color than it is (Apple say it is rose gold, but it’s actually silver) so I guess at some point it has been re-cased.

Everything else on the phone works fine including the 4G and wireless. Can anyone suggest what might be the issue with it?

Thanks.