Refusing a refund after incorrect goods sold

In November 2017 I purchased goods to the value of over R12000 and was satisfied with the service as the staff was excellent in store however one of the consultants who had assisted me on choosing some stuff for my bathroom neglected to tell me that the shower head was not going to work in my bathroom and yet he knew ad I mentioned to him that I still have the old geysers in my house, when I got home we fitted the shower head and it was not working and the plumber said the reason for that was due to the fact that I did not have a high pressure geyser and I told him that I had told the gentleman that I don't have a high pressure geyser and specifically asked him if it will work and he assured me it would, on returning the item as it is not able to work, they blatantly refused to take it back as it was not in it's packaging, however my point I am trying to make is that I told the guy I don't have a high pressure geyser and asked him twice if it will work and he said yes, and now I am a loser of R250 of a shower head that cannot be used and this makes me angry as I spent so much money at there store, deeply dissapointed...??????????????????