SAP Blanket PO with agreement, when the valid to date has passed, why is the system still allowing to procees with Receiving/Service Entry Sheet?

The Issue

For certain materials/services, agreement blanket POs has been set with the vendor where the prices are fixed for a certain period.
However, once the period is over, the system is still allowing receiving/ service entry sheet process.

The Solution

Currently, the system is only treating this as a Warning, which means that even if the valid to has passed, users are still able to proceed with Service Entry Sheet or Goods Receipt.
It is possible to change it to Error Message where it wont be possible to proceed with Service Entry Sheet / Goods Receipt. This can be done in SPRO --> MM --> Purchasing --> Environment --> System Messages