Bad service and processing

On the 20th July 2024, my wife and I went to Bradlows Southgate branch to buy a Conti 300w Power station, which was on special, for R999.97. We were given two options since they didn't have it at the store or any other store for that matter. Options were, either delivery at a fee or collection at Bradlows Ware House. We opted for collection, Tuesday the 23rd July when I’m off. Cool, paid and was given a collection document signed by Eugene, branch manager herself. Today, 23rd July , on the day of the collection, I’m being told it’s sold out and there is no stock anymore. What kind of BS is this? I paid for this product, got a slip and agreed to collecting it today. Why was the product paid for not reserved?