WiFi and Bluetooth not working

Hi, my WiFi and Bluetooth no longer work on my 6s iOS version 11.2.1. It says Bluetooth Unavailable. When I try to connect to Bluetooth the phone freezes. When I try to connect to WiFi it says ‘Unable to join the network’. It also says Update Apple ID settings but won’t let me. Comes up with ‘Verification Failed - there was a problem connecting to the server.’ It won’t update or restore the phone through iTunes recovery mode. It try to update and restore but says ‘iTunes could not connect to this iPhone. An unknown error occurred 0xE8000015’. When you look up the model it shows it as MN0W2B/A. A while ago I took the phone to an Apple store in London and the bloke reckoned the antenna was broken- that the Bluetooth and WiFi operate using the same antenna. It was outside it’s warranty so he said I’d have to get a new phone as Apple don’t replace antennas. Any assistance gratefully received. Thanks