Won't refund on faulty DI Resin

I purchased 1kg of DI(Deionising) Resin from H2O international in Fourways.<br> I use it as a final stage after the membrane to reduce my TDS from 7 to 0.<br> My old resin lasted over a year and still reduced it to 0 until recently.<br> <br> This new resin of which I only used about 300g increases my TDS from 7 to 10. The old resin I replaced did a better job since it increased it to only 8. Of course the whole purpose of using the resin is to bring the TDS down to 0. After many tests and cleaning to confirm that it is in fact the resin and not something else increasing the TDS I called them to report the issue.<br> <br> The person I spoke to was not very knowledgeable about DI Resin and it's purpose and made suggestions that are really stupid such as putting the resin stage before the membrane or adding a 2nd membrane instead of resin. He also suggested flushing my membrane(which is still new and produces 7 TDS water).<br> <br> They were also very expensive at R190/kg where I can get the same quantity for less than half the price online.<br> <br> However now he refuses to refund for this defective resin. Says it's a consumable and taking it back will contaminate his products. Even the 800g unused portion he wont refund.