The first thing i do when i recieve the brg approved email is look at the actual confirmed rate. The actual confirmed rate on the email is the rate i show to the hotel and is also the rate the hotel will charge me.
Should there be any discrepancies upon reading the email, then i can easily contact the brg team to have it rectified prior to my arrival - with an email document showing the correct brg rate.
Personally if this happened to me, id let it go and look at this as a lesson to always double check all important info on the email.