ppi claim

i just recived a letter today saying i have won £2294.87 in compensation from halifax , they also state that they will refund my account with this funds and reduce my monthly pyments with the rest as the account was in arreaers , however can they do this ? im in a protected trust deed just now ,are they within there right just to pass these funds on to the 3rd party who has bought over this debt . if im in a trust deed they have already accepted an offer from mytrust deed to pay this off , so not sure where i stand with actually asking for the money i have won back to myself ?