How to delete or change Item on Sales Order that has a Prepayment

Several Sales Orders were made with 100% prepayments that won't actually ship for months, but now customers want to change which item(s) they are purchasing; however, because of the way prepayments function in NAV the prepayments were assigned to each line, so when you try to change or delete a line in the order we get the following error:

 

Prepmt. Amt. Inv. Excl. VAT must be equal to '0' in Sales Line: ...

 

...and then if I try to change the "Prepmt. Line Amount Excl. VAT" on the line it gives the following error:

 

Prepmt. Line Amount Excl. VAT cannot be less than {amount in prepayment invoice} in Sales Line Document Type='Order',Document No.='{####}', Line No.='{####}'

 

I tried to create a Credit Memo, but you can't reverse lines from the sales order if it wasn't shipped yet, and it seems awfully silly to add Item Tracking info and ship that Item in NAV just to be able to return it when the item never actually went anywhere. Is there any way to easily remove or change such an item in an order with prepayment and how?

 

Thanks!

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