Makro Polokwane's refusal to reimburse

Good morning

I made an online purchase of three items to the cost of 14400, on the 22nd of November from Makro in Polokwane. On the 23rd November, I collected the items but changed my mind with one of the purchases, that cost about 1100. I returned the particular item to store and was given a store voucher to use. However, the item I wanted was only available online and I returned the voucher back to store without using it. The store promised to credit my bank account within 7 days, but have failed to do so. I have been taken from pillar to post without any help.