I see. Although our protocols dictate we check for VDSL synch, and that the dial-tone also works over the chosen 'Tie-pairs' at the Cabinet. If they don't and nothing can be done on the day, we generally leave the circuit running on ADSL as before.
Of course, I haven't got a clue what has happened with your particular circuit, but it does sound like a wrong termination in the Cab ?