Finally

At last. The Viettel technician made a house call at 9:00pm to rectify the broadband connection.
Know what he did?

Accessed the D-Link setting.
Punched in the user ID and password.

Voila. Sigh, why couldn't they just give me that earlier. I would have been in weeks back.

Anyhow, many thanks to Ms. Giac for making all those calls and get this thru. She can see how important this connection is to me.