A common way to get cellular data is by using the command:
netsh mbn show readyinfo * | findstr SIM```
If you can run a script in the SYSTEM context, you can use the "MDM Bridge WMI Provider" to get some deeper insights... (MDM Bridge WMI Provider - Win32 apps | Microsoft Docs).
The required information is coming from the "DeviceStatus CSP" (DeviceStatus CSP - Windows Client Management | Microsoft Docs) where you have "CellularIdentities" which includes:
- CommercializationOperator (Telecom Provider)
- Roaming Status
You can use the following PowerShell command (running as SYSTEM) to get all these Information:
Get-WmiObject -Namespace "root\cimv2\mdm\dmmap" -ClassName MDM_DeviceStatus_CellularIdentities01_01