Repair Center

I am not happy with the repair center.

I bought my phone March 2021 and I believe it's still under warranty as it's still within the 6 months. I took my phone to Cell C as I was having network work issues their sim card was not working. The Reptair Center comes back and say I must pay R2 148 which included the repair in g of the screen which is something I did not request. Now I am forced to pay that amount as they fix everything that is broken on the phone. The simcard thing is not my fault it's a technical thing. How is that I have to pay for something I didn't ask for and for something that is not even my fault. The lady I spoke to just said the repair center fixes everything that is broken, even though I didn't ask for?