Apologies if this has been addressed before

Client just had £150 taken direct from earnings ref an old tax credit debt from 8 years ago, and it looks like this will be taken from wage each month from now on.
when overpayment happened 8 yrs ago she rang HMRC to be told not to worry, they would look into it
As she heard nothing since she thought the issue was closed.
Now DWP have debt and are recovering
Too late to appeal
Is anything that can be done here? Its manifestly unjust
Thanks
http://dlvr.it/RWQpnp