We are converting the sales order with freeze prize as 'Y'.We are importing pricing for the sales or

We are converting the sales order with freeze prize as 'Y'.We are importing pricing for the sales orders from the source systems as it is.But Client has a requirement here that they want to add a sales order line to a converted sales order.But since Freeze price is Y on the converted sales order ,we do not have any strategy or strategy assignment on the sales order .So how can we add sales order line to a converted sales order with freeze price as Y?