By default, the mobile data connection for the Internet on the Samsung device is turned on, but mobile data can also be turned off manually. On Samsung dual SIM devices, only the mobile data of the selected default SIM card can be turned on/off.

Note: Mobile data can also be switched on/off using the quick settings.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Connections
Step 3:  Tap on  Data usage
Step 4:  Enable or disable  Mobile Data
  1. Open the Settings
  2. Tap on Connections
  3. Tap on Data usage
  4. Enable or disable Mobile Data

Samsung Instructions