Iphone 13 battery replacement under warranty

I have purchased an iPhone 13 in April it was a pre-owned device , and it started to give issues with the battery. The battery was detoriated at 78% and every time i get the software update it would reject the battery . And inside the box that came with the device there was a card with the warranty detailing that the device is covered for 12 months . But when i took it in for the repairs to Makro of which they sent it to Vodacom i was informed by Vodacom that my warranty was forfeited due to the cracked rear glass and it had a network problem as well. But i purchased my phone i was never told that if the rear glass is cracked they won't be able to repair it . And they can't even quote me for the new rear glass and repair the battery . Vodacom is refusing to fix my iphone 13 battery of which the phone says it's not original battery.