Poor service and questionable product

Very bad customer service! Bought a Samsung S20 Ultra cellphone online, for collection. Was informed there was only 1 left and they agreed to keep it aside. Drove 140km to collect it and in store opened the box to find the battery had burst. So they fetched another one and again the battery had burst. So in total they had 4 of these phones and all burst batteries. They could not find another on their system so I tried negotiating a deal on a more expensive phone, but they only offered me R1k off. I opted for a refund and was informed it would take up to 2 weeks! Why? They got the payment within a day, why can they not refund me in a day? Not sure I trust this company or the products they sell.....