Changing the purpose of a Local L/C (Purchase Confirmation) due to converting finished product raw materials to domestic sales

I am wondering if it is permissible to change the purpose of a Purchase Confirmation after it has already been issued. Here is the situation: Company A sold raw materials to Company B, issued a Purchase Confirmation, and issued a zero-rated tax invoice. Company B originally planned to use these raw materials to manufacture finished products for export to Company C, but due to difficulties in exporting the entire quantity, they now find themselves in a situation where they must sell part of the stock domestically. In this case, would there be any issues if we apply to change the Purchase Confirmation a few months later and handle the portion converted to domestic sales by voluntarily paying the applicable taxes (VAT, etc.)?