RCS ignoring an arrangement and debiting a pensioners money, really, all of it?

My mom who is a pensioner has a loan with RCS. She mad an arrangement to pay them via money market on a specific day as they never debit her on correct dates, they now have enforced a debit order taking her whole pension to pay her loan and ignored the arrangement. She didnt receive a debicheck auth, nothing. This is pathetic when a financial instiution does this.