Bad treatment as a customer and rights violention

I bought external hard drive 2tb in the lydenburg store and never used it until I bought my new laptop and It didn't work and then I went back after 2 weeks for help they can't diagnose a problem and works only on pc. No signs of damage nor viruses but was told that they can't refund me since the warranty of 7 and told me to leave, they never gave me options on what to do and now I'm stucked with a useless thing