Pick and Pay hyper market and sinotec bad service

My brother in law purchased in Sinotec TV in 2016, with a 5 yr warranty. In 2018 I purchased the tv from him. In November 2019 the tv would not switch on, my brother in law said he would take the tv back to pnp however he no longer had the till slip and the manual till slip and the box because he moved and got rid of things. The sales people at PNP said they will send it through to sinotec for repairs as it’s still under the 5 yr warranty. After numerous.l calling speaking to Shaun and Remola from hyper market they advised that the tv is not under a 5 yr warranty and that we have to pay for repairs. I was told that they never had the 5yr warranty offer in 2016 and introduced it only in 2018. This is ridiculous as the sinotec website hosts about their 5yr warranty on their products. We still do not have the tv back it’s at the hyper market in Ottery Cape Town and Sinotec refuses to repair. This is disgusting service from both companies I just need my tv fixed!!