Charged R1200 for software upgrade

I bought a Cellphone for R2000.00 at Sterns in 3 months time i took it in for software upgrade and because my screen was cracked i have asked them to replace it, my phone is insured and is only 4 months old. I was told to pay R1200.00 for a software upgrade and a cracked screen Why am i paying insurance and my phone is still under warranty!!! the lady (Zuwayda) i spoke to this morning said she can not help me. And the one who assisted me while handing my phone in was (Andea) she did not even capture on the system that the screen needs to be replaced she only wrote (Software upgrade). Which basically means i am charged R1200.00 for a software upgrade and it's been four weeks i'm still told i have to wait for my phone to get back to the store otherwise they can't help me. This is **************** i am not sure if i will get my phone back!!! I am very disappointed with their service and still can't believe that my warranty and insurance are not even taken into consideration for this matter.