Wrong HBO Max account got attached to my streaming through xfinity

When I activated HBO Max through my streaming bundle it accidentally went to a family members HBO Max account. I need to change it to be my own account but I cannot find any way to do that. HBO Max won’t let me unlink Xfinity and Xfinity won’t let me unlink HBO Max. 

How can I change the HBO Max account my Xfinity subscription pays for?