Being quoted for the phone that is stil under warranty

On 28 June 2023 I took an iPhone 13 128GB to vodacom repair shop in Hatfield Pretoria for repairs.The phone switched off by itself on 27 June 2023 around 03:30pm.I arrived at vodacom Hatfield repair shop on 28 June 2023 around 11 am to book the phone for repair.The phone is practically new and still under warranty because I took it on a contract on 06 may 2023.This morning(29 june 2023) I got an sms from their repair center asking me to either accept or decline the quote.I was surprised because the phone is still under warranty so why are they quoting me.When I called them they accused me of having had unauthorized repair done on the phone and the amount they are quoting me is R10000,00.I never did such a thing.How can I take a new phone somewhere to get it fixed while I know very well that I'm covered for warranty.All I want is for vodacom repair Hatfield Pretoria to fix my phone without quoting me because there is no physical damage on the phone. My name:Brenda Cell:***