Out of stock after dispatch notice received!

I purchased a generator through groupon. I soon received a dispatch notification with a tracking number. <br> When I followed up with the tracking company 5 days later, I was told that they were out of stock.<br> After a week of no response from groupon, I finally found their phone number, hidden in the website. I was told that the courier company was wrong and that I would soon receive an email clarifying everything. After another few days of no response, I was assisted by a very helpful lady who followed up and confirmed that they were indeed out of stock. I was refunded shortly after.<br> How does this work, how do they advise customers that goods were dispatched when they are out of order. No apology for the inconvenience, no explanation, no compensation for having a customers money for a month = someone who will not use groupon again.