There are three ways you can try to get a decision changed -
-You can ask the DWP to revise their decision. You can ask for a revision for any reason at all.
-You can ask the DWP to supersede their decision. Decisions are superseded if there has been a significant change in your circumstances since you first claimed or if the DWP has made a mistake in deciding your claim.
-You can appeal to an independent tribunal.
Most DWP decisions are not given with any reasons. Claimants are entitled to ask for a written statement of reasons during the 1 month "dispute period" after the decision was sent.
The Decision Makers' guide states that the written statement should -
Time limits
You should ask for a revision within 4 weeks of receiving the DWP decision (6 weeks if you ask for a written explanation).
There is no time limit on asking for a decision to be superseded.
You should ask for an appeal within 4 weeks of receiving the original decision.
or
within four weeks of receiving a decision on a revision or a supersession (6 weeks if you ask for a written explanation).
Complaints
If you are not satisfied with the service the DWP have given you, you can download the Disability and Carers Service's customer information leaflet which sets out how you can make a complaint.