My cats microchip is under someone else’s name..

So I adopted a cat yesterday from the shelter and I went to register her microchip online and it said that she’s already registered to someone else? I checked and made sure that I put in the right number. I contacted the girl that fostered her and she said that when my cats brother got adopted that new owner accidentally put in my cats number so now she’s registered under that guy? How do I go about fixing this?