Check APN settings
If you don’t have a network with your SIM card, this may be due to the APN settings. With this setting, your S8"dreamlte" knows which network it should dial into at best.
APN is the abbreviation for Access Point Name. The best way to find out is to go to your mobile operator’s help pages on the Internet. There you will find the APN data. Now you’ve to match this data with the settings in the menu of your device.
Device > Settings > Mobile networks > Access point names > APNs
