Poor and disgusting customer service

I bought two shower columns from them around July towards month end. I went to collect both of them. My plumber installed one in one bathroom and there was no leak everything was good. We discovered the problem with the second one it was installed and was leaking on one of g e knobs immediately on installation. I took video of same and sent it to the shop and write an email complaining of same. They sent a very ************* technician to come and check it. He told me that the plumber did not install his pipes properly when he talks to the plumber he gives a different story. He confessed to him that it's not only the knob that is leaking that has a problem but all the knobs and they need replacement. This was confirmed by him stripping all the knobs from the shower. He left and promised to come back. As we realized when talking to plumber that there is a problem I told them to replace it as it has problems. They end up agreeing to replace it and delivered another one and take one with problem. Even the one brought as replacement it was installed and it's leaking as well. I also took video of same and sent them together with an email. Since I advised them of that problem they are ignoring both my WhatsApp and emails. They are silent. Romeo told me Wednesday that they will contact me but nothing is happening. They ate delaying my plumbing progress. I have requested the to come and collect it and refund me the money paid as it is. Now they are silent they don't want to take responsibility. Kindly assist please.