Purchasing a phone from iStore Woodlands

I bought an iPhone 11 from the Woodlands iStore. My iPhone SE trade in, according to their computer which I saw, was R4500. The agent told me that if I wanted a charging cable. they would subtract that amount from the trade in price, but neglected to put that on the invoice. The trade in was listed as R4350. The cable that came with the phone is of no use to me because it does not have a USB. When I asked for a cable that fits my iPhone charger,I was told that I needed to pay a further R399 for an adapter. Why make me pay for (which they now deny) a cable that is of no use to me? They are also not willing to give me a refund for the cable. I no longer trust this business and certainly wil not do business with them again - especially in the light of the fact that I could get the same phone from Takealot at substantially less. But I thought I would get better service from iStore, which I didn't.