Purchase Order Workflow

We are experiencing some difficulty in the PO process - anyone else struggling?   

Our background:
1)  We have enabled the Advanced Receiving feature. 
2)  Our PO process -
     a) Employee inputs purchase request.
     b) Manager authorizes/rejects the purchase request.
     c) Employee receives/closes the purchase order.
     d) Accounting bills the purchase order.

Problem:  We pay our bills using NetSuite.  Each bill requires a purchase order.  Our Accountant inputs a purchase request for G&A bills.  Then he opens a bill and pays the bill for the purchase order.  The purchase order just sits at "Pending Receipt" forever. 

Question:  Is this because of the Advanced Receiving feature?  What features are affected by the Advanced Receiving feature?  (We are a service based company so we never ship physical items.)  How can we require the PO be received before opening a bill?