Confirmed order not delivered

I have two problems; 1. I purchased a Ryobi compressor online and received a message from Builders that my product is ready for collection at your Northriding store, my initial order was for Little Falls which is closer to where I live. I drove all the way out to Northriding to go and pick up the product only to be told that someone was about to give me a call to tell me that they don't have stock. This was unacceptable because when I as a customer receive confirmation that I can go and pick up my order I expect it to be there. I've been dealing with Stanley Manuel from your customer support but I'm yet to receive any confirmation that my product has been ordered and that I'll receive it. 2. The second problem that I have is that an hour after I paid for the product online you send me an email saying that I qualify for a 15% discount off my 1st online order, this means that I could have gotten R300 off, now I'm offered a 15% off voucher which defeats the purpose, as I'm never going to be buying any large items from you again so I'm losing out. I guess by the time this is sorted out you're going to tell me that I can go to the store to collect the product, which is also not fair as you've already wasted my time and petrol.