Dear Samsung Member,
Greetings from Samsung Customer Support!
As per your concern kindly visit this mentioned link to resolve your issue: https://www.samsung.com/in/support/mobile-devices/samsung-galaxy-smartphone-how-to-optimise-network-...
In case the issue still occurs kindly visit the service center for a physical inspection of your device and they will guide you regarding the replacement of the device. You can locate your nearest service center with this given link: https://www.samsung.com/in/support/service-center/
Samsung Customer Support