Bifurcation of service PR activity qty in service PO

Hello experts,

My client has one requirement for below scenario (could not find the solution in various online search).

1. Service PR has two line items

2. Each PR line item has two activity items

3. Single service PO created for both the line items of PR

4. Partial qty received (service entry posted) against each Line item of PO (i.e. 4 activity lines of 2 PO line items)

5. Now, new service tax code is to be used for remaining (undelivered) qty.

6. Please suggest how to short close existing 2 PO line items ( 4 activity lines)  and create 2 fresh PO line items (4 activity lines) with new tax code for the remaining qty (activity qty).

thanks