Iphone 7 Wifi Not Working After IOs update

Hi All,

I updated IOs 15.6.1 today and after that immediately my phone WiFi and Blue Tooth buttons became gray and not working for making Wifi/Blue Tooth on or off.

Several times, I switched off the phone, reset the phone using power on/off & volume down button pressing together for 30-40 seconds till the apple sign shows off, reset the network settings, etc.

Also i showed the phone to local apple service center and he is saying there is problem with hardware and suggesting to replace the complete phone hardware. I am unable to understand how come there could be problem with hardware when both these systems were working fine just before the software update and there is no physical damage or drop off of the phone.

Can anyone suggest how to resolve this issue?