Need to Apply a global procurement within multiple ledgers and legal entities

Summary:

I would like to address the global procurement aspect in Oracle, which states that the sold-to legal entity and the requisitioning business unit must be distinct. Although I have completed all the requisite setup tasks, I am still unable to modify the sold-to legal entity. To illustrate this, please consider the following scenarios for two Business unit A & Business unit B:

Scenario 1:

1- Purchase Requisition (BU A)

2- Purchase Order ( BU B)

3- Receipt (BU A)

4- Invoice (BU B)

5- Payment (BU B)

Scenario 2:

1- Purchase Requisition (BU A)

2- Purchase Order ( BU B)

3- Receipt (BU A)