Nedbank refund

Hi, March was my last month to pay my personal loan, and we get paid earlier, I then transferred the outstanding amount to loan account hoping that maybe their system will update, it was on Saturday, on Monday 25 March they deduct the instalment, I phone them to inform them and they promise to refund me in 3 days, I ask a Favour to priorities the refund as my debit order going on 25 of every month and they agreed, Tuesday 26 no money, Wednesday 27 still no money, I phone I gain and they say money will reflect on Thursday 28, till today there is no refund, not sure if this will take 31 days to reflect. Please advise as to when will I get my refund.