Unable to Delete ERV (Exchange Rate Variance) from Cost component Mapping

Summary:

Initially, our client requirement was, ERV (Exchange Rate Variance) should be part of the cost. So, while setting up Cost organization we added ERV in cost component mapping and share the same cost element which is set for the ITEM_Price. But now the requirement changed, the client wants to eliminate the impact of ERV from the Item cost from July-23 costing. So, how can we update the cost component mapping to eliminate the ERV costing impact as the system does not allow us to update because around 4 months of transactions are already processed?

We need an urgent solutiontor this.