Ordered item they didn't have, now I can't get my refund after canceling the order

I ordered an item which they had advertised but didn't have stock of it. I had to wait for long and they didn't even let me know what was causing the delay. I eventually got in touch with them to find out what was taking so long and their response was so unsatisfactory.

I eventually had to buy the same item from another store,which was delivered the following day. As a result, I had to cancel that order, which they said they were gonna charge me 15%, for what I don't know cause if they had the item I wouldn't have cancelled it.

Now I've been going from pillar to post to try and get my money, and all I can get is automatic replies. Their landline doesn't even work. I don't even know why I bought that nonsense of a store. I'll encourage people not to even think about buying from them.