Disappointing customer support and delay in delivery of order

I have ordered twice before from Showpspace and the delivery was quick but the latest order I placed left a sour taste in my mouth and I doubt I will be ordering fromthem again. I ordered 2 items only to be emailed about 3 days later that one of the items I ordered is no longer in stock but there was an alternative I could opt to get instead but that I would have to pay the difference between the originally ordered item and the alternative, I was then sent an invoice and I paid the difference and sent them the POP, it is now over a whole week since I paid and I have not received my order, the support team is very slow to assist customers and they do not reply to emails. I am very disappointed in Showspace especially since I was starting to be a loyal client.