3 month old Hisense TV broken and refusal to repair

I got a Hisense UHD TV from the Grove Mall. 3 month after the purchase the TV screen is covered in white line. I lost the original receipt but have proof of purchase from my bank and a reprint of the invoice but am told by the store this is not good enough as proof of purchase for the TV to be repaired.

I have now had to engage lawyers to have my 3 month old R7000 TV repairs.