Incorrect goods sold

In November 2017 I purchased a showers head from brights staff was excellent in store however the sales person who assisted me was great however I am dissapointed that after asking him about 3 times what shower head I could purchase ,explaining to him that I bought a fancy shower head but now it's not working also telling him about thrice that I still have the old geysers installed and need one of the old types of shower heads and he insisted that the one he is sowing me is the one that will work, to my surprise when I got home and switched on the shower to test it, the thing was not working and now they are refusing to take it back as it has been opened, how else do I see it the thing is working or not if I don't remove it from it's packaging to test it and that just totally upset me that these shops takes ur money so easily but when I wanted to exchange the item, they refused, also I bought a vacuum which is not working properly which supposedly has a 2 year guarantee which is more problematic than anything else, but they also refusing to take it back, so I should just be a loser of R400...???????????????pathetic for such big stores to treat people this way...I am extremely annoyed that the sales guy promised this vacuum is a good one for the purpose that I would like to use it, what a lie....