Defective iPhone 16 ProMax

I purchased an iPhone 16 Pro Max via online shopping with Vodacom. The waiting period, as expected and explained was very long due to shortage on stock of said device. After 1 month the device arrived (November 2024), however the device was giving issues with Network, constantly searching for network. i took the device to Vodacom repairs and they did some setting changes and said the device should be fine. the device was giving more problems after a week returned to Vodacom and again same issue was reported - The device keeps searching for network it drains the battery and uses excessive data by continuously searching for network. no matter what sim card is inserted into the iPhone 16 ProMax it does the same. I was asked to book the device in and that it needed to be sent for repairs/assessment to determine the fault. The device is not even 3 months old and had this problem from the very first day of use. When asked to replace the device the response is no it needs to be replaced within the first 14 days of receipt but the defect was reported within the first 14days but only settings adjustments was done and there was still no change on the defect.