Bad service

I am very disgusted by the way they treat their costumers I alway purchase from them they made the mistake and delivered the wrong item to me and sold out the item I already paid for when it was available now they don't want to own up to their mistake and give me what I purchased, all they said was sorry we will refund you. This is not how you treat your customers really now and I waited three weeks for them to deliver the item I bought online from them then they still send me the wrong thing now they want to tell me that they can't give me the item I bought from them they say it's not available. I have my receipt for the extractor fan I bought from them I checked on their website they have a extractor fan same one I bought different price I told them because they made the mistake to send the wrong item to me which led to my item being sold they must give me the other extractor fan that they have online they are not answering my complaints or even owning up to their fault