Sorry to hear you had the same experience. It's extremely poor form on their behalf.
While it's tempting to chalk it up to something sinister, I'm wondering if it's just flat out ineptitude and poor business skills. It's possible that they don't read their emails, or read them but get distracted and forget there's an action to carry out. It's also possible that their inventory management is terrible, so they don't realise that they have something to ship out to someone -- until that someone forces a refund due to their repeated lack of response, which draws their attention to it. Then instead of saying sorry, admitting fault, and trying to make good with the customer -- they figure the trust is already broken, continue the wall of silence, find the stock in their inventory and sell at a higher price on eBay.
Sinister or incompetent, the message is the same. Don't buy from them.