Unauthorized debit order

I have a policy with Sanlam. The agreed date for my debit is last day of the month as it's my payday. They deducted on the 15th December 2020 without my knowledge and I have incurred fine from the bank as I didn't have money for that debit. I phoned and wrote several emails complaining they didn't come back to me. I need them to pay the debt incurred from my bank. I'm a retired old woman and find it horrible to be treated this way