Standard Bank taking early debit orders without permission

I received an SMS from Standard Bank on the 12th of December stating for my convenience they would be debiting my homeloan from my account on 14 December 2018. I phoned them immediately and informed them i would only be getting paid the following week and they were not to debit my account early. On 14 December they debited the full amount form my account regardless. After numerous phone calls and promises i have still not received the refund from Standard Bank five days later. I feel this is contravention of the contract i have in place with Standard Bank and ******* as they too money out of my account without my permission after I explicitly instucted them not to.