Defective plumbing product and dismal after sales service

Awful experience with a defective plumbing product and after sales service. I purchased a Lusso "Savio" (in house Builders brand) basin mixer earlier this year. I personally installed the mixer and all seemed good. However, the tap dripped from day 1. That drip has become worse as the months went by and I decided to approach Builders for advice and spare seal/washers. Here the story becomes bizarre. After an initial interaction with staff at the plumbing section at Builders Cape City at North Gate where I was asked to bring the product box in so they could identify the model and supply the correct cartridge, things went downhill. I duly comp**** and arrived with the empty box and tap model name - to be told that they were unable to assist because their spare "cartridges" are not marked or barcoded to allow them to supply the correct one for the tap that they sold me, or indeed any other tap they sell. The remedy is for me to switch off the water ( in my house there is no isolator tap for the mixer) and bring the cartridge in so they can visually identify which part fits. This is farcical and worthy of am SA government department. To make matters worse, the manager in this department tried to defend the terrible spares inventory system they have and made out that it was perfectly normal due to the wide range of taps they sell. Utterly unbelievable. So we have a ******* defective tap and on top of that dismal after sales service and spares availability. I have previously been stunned by the poor service from staff employed at Builders but this is a new low. Boycott Builders is my new motto.