Please note that device speed may vary based on multiple external factors. Kindly follow the mentioned steps to resolve the issue in your device.
1) Ensure that network frequency of your device should be selected on Auto-mode.
Menu>Settings> Connections>More Networks> Mobile Networks> Network Mode> Select Auto mode (GSM/WCDMA/LTE).
2) Search for the Network Manually
Menu> Settings> Connections>More Networks> Mobile Networks> Network Operators> Select Manual Search.
3) Perform the reset network setting (Go to the settings>>general management>>reset>>reset network settings).
4) Insert different SIM card in your mobile and check if the issue is resolved or not.
If still issue persists then we would suggest you to contact your service provider.
For further assistance, register your concern in Samsung members app (click on “+“icon>send feedback>Error report/ Ask Questions).
Team Samsung Members