Newborn Being Billed As Themself instead of Mother under UHC

We had a child on Dec 26th, I added my child to my insurance since it’s a qualifying event. From there though, they got billed instead of the mother, who’s out of pocket max was met so it should be 0 for everything. Should I fight back and say that we never gave the hospital our newborns insurance information and to bill the mother instead for the 30 days that it’s allowed?