Had one two weeks ago. As we were boarding I sat down in my middle seat (it was a last minute assignment thus the middle seat) and simply took a screenshot of the pairing (from EZ CCS) and a screen shot of my mobile boarding pass (from the United App) and sent to [email protected]. In the subject line I put my file number/DH flight#/pairing #. This was on a Tuesday. My middle seat add pay was reflected on Thursday. Easy