Don't want to pay refund owed to me

On 30 June Chubb debited my bank account for an amount of R1,638.75 in respect of work they had done repairing beams on our property. They did not notify me of this so I mistakenly paid them as well for this amount on 17 July from the same bank account. I discovered this error soon afterwards and am battling to get my money back. Every time I phone I am told the refund is being "processed" with about ten line managers required to approve the refund. They were very quick to debit my bank account on the same day the work was done and did not even send me an sms notifying me. I want that money back NOW. If you don't want to pay it back I will give you a month's notice and take my business to North Natal Security. You might even wind up in COURT and have to pay my legal costs.