In Windows 8, the "Forget this network" option is missing with some carrier specific mobile broadband connections.
Example steps to reproduce:
1) Click the network system tray icon.
2) Click "Mobile Broadband 3" and select "Find More" then "United States" and click "OK".
3) Right click on a mobile broadband connection, note that the"Forget this network" option is missing.
This behavior is by design as Windows does not provide the option to "Forget this network" if the Mobile Broadband profile is provisioned by the carrier. The option only appears when a custom or user profile is created.
forget this network, mobile, broadband.