BRM charge override

I wanted to know how to override the charge/rate information in BRM batch rating (pipeline)

When pipeline gets CDR`s it rates them using associated rate plan, let say the rate plan is configured to charge VOIP calls per minute $ 0.5.

but during the rating time i wanted to change this per minute charge to $0.3 by looking some customer attributes.

How can I achieve this in rating?

Is there a way where we can update the charge packets / anywhere to update the new rate ?
(OR)
After the rating of EDR, is there a way to update the final charge value to new charge value ?