Debit order from bank account I never signed for (or gave details)

I joined Multiply back in 2013 when I joined momentum health. The fees were deducted from my bank account I provided and signed for. Two months ago a debit order went off on my wife's bank account that had my Multiply Reference number. Some how they manage to change the debit order for the multiply fees to go off my wife's banking account. She never provided Multiply with her banking details or ever signed a form that they can take the Multiply fees from her account. Where did Multiply get her banking details?