Damaged Isuzu radiator

I had my radiator changed & a new one put in by Wynland Motors in Stellenbosch. After 3 to 5 months I noticed mty bakkie was getting hot & when going to the garage they told me there was no water in the radiator. I took my bakkie to another well known mechanic & was told when they changed my radiator that this "new" one had 3 holes in it. I took it back to Wynland & they said they would send it off to Corenet to be evaluated. The answer i got back was "" Under pressure testing a leak was from the core. white residue on the header-plate & on the inside of the tank & discoloration that are signs of Electrolysis Chemical Corrosion". Based on this they rejected the claim for a refund. I would like to know what my previous radiator was in the bakkie for 16 years & never had a problem. And now within 3 months there's aproblem with this one? This is absolute ******* & I feel this is typical ducking & diving tactics from people who think they con talk ******* to someone who is not a mechanic? This is disgusting & I will definately let people know what bad service these people give!