When the network settings are reset, the default settings of the factory settings are loaded. The network settings include all settings concerning the WLAN, Bluetooth or the network (mobile radio) itself.

Note: Resetting the network settings cannot be undone. Saved WLAN passwords or connected devices are irrevocably deleted during the process.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  General management
Step 3:  Tap on  Reset
Step 4:  Tap on  Reset network settings
Step 5:  Confirm with  Reset settings
  1. Open the Settings
  2. Tap on General management
  3. Tap on Reset
  4. Tap on Reset network settings
  5. Confirm with Reset settings

Samsung Instructions