Outright dishonest and ********

I purchased an iPhone 15 pro max 512g online from iStore. My order was accepted, I paid the price in full, and received an email confirmation. A few days later, after hearing nothing more, I queried the order, only to be told that the phone I had ordered was no longer available in South Africa. So I downgraded to the 256g version and was told that I would receive a partial refund of R5k. I received email confirmations and while the phone was received, the partial refund was never paid. I have phoned the iStore several times and am always told to give it a few more days. In the meantime something like 14 working days have passed - nothing doing.