New Samsung Galaxy worked for less than a week

I purchased a Samsung Galaxy S5 from the Altech Autopage Cellular/CA Cellular Holdings store at Nicolway in Bryanston on April Fool's Day - must say something! Within the week the phone was freezing and then continuously rebooting. It was the Easter weekend so I returned on Tuesday April 9 - eight days after purchase. They would not refund or replace the phone as seven days had gone by. Instead they wiped all the software off and reinstalled which worked for about another week until the problem started again. I was then told to take it to the Altech Cellular branch in Sandton City which I did on April 21 where they promised it would be returned in five working days. I do have this in writing on a customer repair order (002221). On Monday I still had no phone and no feedback so went to the store and was told Alicia would contact me on Tuesday with a quote to repair the phone. Huh? Obviously Samsung aren't even aware of the problem but it is similar to buying a new car that has serious problems and the dealer making no effort to remedy the problem.