Price phase &3 for material &1 &2 not deleted; it is already activated

What causes this issue?

The price phase with the start date &V3& for material &V1& &V2& cannot
be deleted because it has already been activated.

System Response

The price phase is not deleted.

How to fix this error?

Create a new price phase with the requried start date and price. Then
activate the new price phase.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.