Unable to Delete an Amortization Schedule

After following the steps from the Help Guide:

Deleting an Amortization Schedule

1) Open the Amortization Schedule under Lists > Accounting > Amortization Schedules

2) Go to the Created From field > Click on Bill

3) Go to Expenses and Items tab > Expenses subtab > Click on the first line that has an Amortization Schedule

4) Click on Make Copy Button

5) In that new line, Remove the Amortization Schedule

6) Go back to the original Line > click Remove

7) Save

Doing the steps above , NetSuite automatically deletes the Amortization Schedule associated to the Bill.