I booked my iPhone 12 in at iStore Cresta Mall for a battery replacement

I booked my iPhone 12 in at iStore Cresta Mall for a battery replacement. The screen was working properly when I handed it in. After their assessment, the phone was returned with internal screen damage (ink/vertical lines) that was not there before. I was then quoted over R12,000 for repairs. Instead of helping, iStore keeps making excuses and relying on terms and conditions, even though the phone was returned to me in a worse condition. I am still waiting for a fair resolution.