How to update Rate Type on Blanket

Hello

Recently we've noticed that blankets were created with rate type as User . We expect to follow Corporate rate type for all POs .  Is there any way to change it.

Found following in document :

Entering Currency Information

Use the Currency window to enter and change currency information for purchase orders, RFQs, and quotations.

For purchase orders, you can change currency information until the purchase order is approved or encumbered. Note that changing the purchase order supplier to one that uses a different currency overrides any information you have entered in this region.

   To enter currency information:

1. Navigate to the Currency window by selecting the Currency button in the Purchase Orders, RFQs, and Quotations windows.