Incorrect Cost price

Dear All,

I had created a sales order for 10 MT of Steel where the VPRS condition type picked up 50 INR whcih is the standard price in the material master.When I tried to do PGI after 15 days the Standard price was updated to 75 INR through /MR21.But the material document price is still showing as 50.

How to resolve it.

Regards.