Empty promises and terrible customer.service

I purchased an item off groupon in early April and discovered it was defective when I received it. I then emailed the groupon customer service inbox and advised them of this. I called in the next day as I needed the item urgently for this past weekend. The call center agents made false promises and the one who ultimately kept in contact, Asheeqah, assured me I would have the item by Fri 24April but did not inform me, after I requested a delivery address change that this could not be done. I only received the item yesterday with no response to any of the emails I sent. Shameez emailed me Fri to say I had never sent through a request to change address but when I called the supplier and courier myself on Fri, they had the new details on hand somehow. I was also told last week that as their supplier says the item should work, I am probably using it incorrectly...quite patronising. If they knew of constraints that wouldn't allow them to get the item to me on time, rather advise me but don't make false promises and don't make your inefficiencies my fault.