How to end date/remove suggested buyers and reassigning purchase orders and agreements?

Our team is trying to implement the PDRT and we are currently trying to resolve some of the constraint errors that are returned by the tool. I'm having trouble trying to resolve the following error:

"Purchasing: This person is a buyer on open purchase orders or agreements. Reassign the purchase orders and agreements"

I was able to end date the buyer, but they are still listed at the buyer since this PO is from a date in the past. I'm also having trouble resolving a similar error:

"iProcurement: This person is a suggested buyer assigned to open requisitions. Reassign the requisitions."