What exactly is warranty????

I am disappointed with the quality and service I received from Samsung South Africa. I bought a mobile phone, Samsung A50 last year in June. My phone stopped working in March, it wouldn't touch. I took it to Samsung Mall of Africa to see if they could fix it under warranty as I hadn't done anything on the phone that would damage it's sensor. Freddy, a technician in customer services took in my phone on the 20th of March and promised to call back in 48 hours with the "diagnosis". Long story short, he called called 20th of May and said to me that I have damaged the sensor of the mobile phone and I will need to pay R2400 to get it fixed... Now I didn't get any explanation as to how I could've damaged my mobile device to that point where it would stop functioning. I have 2 other colleagues using the same phone who actually have their phones stop working overnight with no physical damage visible. My phone is fairly new and I really am not willing to pay so much money to get a phone fixed that I didn't physically damage. I am utterly disappointed in a brand that I've always loved and trusted. Please help me out!