FALSE ADVERTI*****T

So not pleased with the online service at Builders warehouse...i purchased a heater online on the 19 June 2020 and i was called back that they currently out of stock at the moment , once item is available they will call and i would have to collect immediately as they don’t have a storeroom to keep he item .Till today I don’t have the heater and i called this morning same lady (Shirley) said they still don't have stock but no one bothered to call and give me options and advise as to when they are expecting stock. She went on to say she doesn’t know either when they will get Stock. This was a store at PROTEA GLEN. I checked for a different heater at a different store Eagle Glen store showed that they have 1 in-store i quickly purchased made instant payment and will collect the item .I just got a call now that they are out of stock and the suppliers says they will have the stock next year I had to cancel now and I’m told for refund I must go to one of the stores. My question is why are the items available online yet they don't have stock is this some sort of false advertising. Why does it allow you to proceed with the payment yet they don't have stock