I have been paying my father's medical aid since inception taken out two or three years ago

I have been paying my father's medical aid since inception taken out two or three years ago. I have never defaulted on paying the medical. Bonitas decides to change admin department that deal with boncap. They change my debit order date in January without advanced notice. They debit my account on the sixth of January instead of 20th like every other month. I later made a payment on 20 January via eft and never missed a payment. Today the debit double the debit order amount and my bank account went into a negative balance. Please fix this or I will log a complaint on the ombudsman to seek assistant.