I have already filed my taxes and didn't give checkbox authority. How i give that authority to my friend to speak to the IRS in my place.

I am only owed the first two stimulus checks. I filed my taxes in March after many years of not having to file so I could receive the first two relief payments.  It's not been 4 months since I filed, the website says no information is available. I am unavailable to talk to the IRS.  I want to give IRS the authorization to speak to my friend and figure out what information is needed to process my return. IRS sent a letter saying there is possible identity theft, I faxed a letter to them satisfying to receive the 3rd stimulus check, but still no information online on the taxes for the first two payments (my tax return). Since I have already filed the taxes would I have to amend them to give checkbox authorization? Or given the possible identity theft assumption does anyone know a path to take?