False advertising

I purchased a grinder from builders and it has a year guarantee on it I only used it twice and it packed up so I take it back to have it replaced. The lady that helped me said I should wait seven to twenty one day and they will call me already the going against what they advertised because it is under guarantee and not warranty. I then received a call this morning from the lady and she say I pay them R309 to have it repaired, but the grinder cost meR319 without vat. Also they did the same thing to my dad two weeks earlier so it’s not an isolated case . They truly misleading there customers and are braking the law…. I’m so furious at them are there no longer any morals in business? Do these big businessmen away with false advertising and get away with it?