Unposting Question

Hello All

I have this question. I have a voucher that was applied to a prepayment fully. I want to undo this because it was a wrong voucher that was applied. Per PeopleBooks one has to unpost first before you can unapply payment. But they also mention if the payment is applied fully, this cannot be done. Unposting a regular voucher that was applied to a prepayment fully is not even available for unpost (based on search view used for unpost). Can anyone recommend what is the process I need to follow or is this functionality broken?

Thanks

Balaji