Adjusted Product Price Applying to Existing Invoices

The client has made a purchase request for Product A at price $100. The amount is not being settled yet.

After a certain time period Shopify admin changed the price of Product A from $100 to $200.

The aforementioned purchase price is being increased from $100 to $200.

Such scenario should not be expected.

The client should have the price kept at $100 despite any price changes in any point of time in the future. How can we avoid such change of price in the invoices/sales that already exist?