Lenovo i3 laptop exchange issue

Have been looking for a laptop for the past 2 weeks , finally saw the Lenovo i5 and a red Lenovo i3 I had been deciding between at CNA Eastgate mall. Last week Friday I went past Mall at Carnival and noticed the i3 I wanted was R5999 by them, not knowing it was also the same price at Eastgate I made my decision to get the i3 because I loved the color, the gentleman at carnival was very helpful and I bought it from them. we didn't open the box as he said all i3s Lenovo they had in stock were in the red finish. when opened the box with such excitement it was the black finish. I went to Eastgate as I work close to them and they said I had to a refund from the other branch and come buy from them. Didn't want the hustle of refunding so I went back to M@ C after work on Saturday and asked them to exchange but unfortunately all their stock they had left was in black. went back to Eastgate and they were so rude to me , spend half a day trying to get them to exchange, the so called manager Dudu said she cant. She told the lady called Hailee I think to check stock and she said I had to wait for Keith. after waiting they didn't exchange and I am an unhappy customer. what do I do now?????