Faulty Goods

I bought security parts from your shop.They didn't work.One staff member tells me to bring them back.I do this but then theres a different guy there.He says he cant swop it as he has no stock.Im staring at 3 new units in the shop, and show him...he just ignores me. I left faulty goods at shop and I'm still waiting from October (Now December) for a refund or new goods....You guiys are just not interested in sorting my problem out, but you have my cash and the goods