Failing to refund back over paid funds

I settled my 2 accounts last week and overpaid them. I requested refund via email sending also proof of payments. After 7 days when i contacted call center, the agent said the funds were processed in the past 24 hrs and will reflect after 24hrs after my call. After my call i waited 48hrs there was nothing. I decided to call and spoke to different call agent and explained what happened, she told me R3500 was processed in the last 24hrs and funds will be avail anytime. I waited for 24hrs and there is nothing. Why it takes so long to refund someone but if 1 is applying for loan funds reflect same day. Are u making interest with my money? Paid up letters have been issued without refunds. Will i ever make business with you in future?