Hi Odeng
Welcome to the forum, you might want to have a look at the following FAQ which explains where everything is
Welcome to Benefits and Work On the forum we have had quite a few posts from members who have been told by the DWP that they cannot overturn a decision made by a Tribunal.
In answer to your question
'how to proceed if the DWP refuse the review insisting that they cannot overturn the tribunal's decision' I am not aware that you can proceed.
Claimants who have been in receipt of the enhanced [rate of both components of] PIP since the judgment date, or who have had a tribunal decision that would have considered the judgment. These cases will not be reviewed.
Gary