12 pro iOS 15.5 boot loop

I phone 12 pro with iOS 15.5 software issue cannot be repaired at storm front Inverness now called select an approved apple dealer apparently. Contacted apple support and offered a repair at over £500. Don't think it's very fair. Anyone got a possible sulution to fixing this issue?

Phone only powers on when . connected to socket or wall by holding power button down. Laptop symbol appears. Connect to mac or laptop and it recognised the phone. Then half way through update the phone turns of and restoring it fails