bad advertising

I purchased a Tony and Guy hair straighter in December 2016 and was told it has a 5 year guarantee. In November 2019 3 years later it stops working. I took it to Gateway Clicks where i purchased it from and get told that it is no longer on warranty and they can change it for another 1 but i need to pay in the difference of R500. What is the purpose of telling your customers 5 years guarantee when 3 years later it’s not valid.