A very unhappy customer

I purchased an iPhoneX on the 3rd of April 2025 at Apple guy the one in Cape Town. I have tried to download the App that I need on the device I had challenges with installing WhatsApp on the device. The following day I reach out to the store they advised I should purchase a new SIM card and I did and same issue still persist. I went to the store again today they checked the settings and there updated what needed to be updated and the issue still persist. The lady that assisted me advised that I should contact WhatsApp as it a 3rd party Application and I did join a chat with the support and the issue still persists. I even created WhatsApp with one of my other numbers that has whatsApp and its till gets me the same error.

I want Apple guy to give me a new device so that I will be able to install the apps I want not making me run around in circle and take accountable you as you mentioned that you have a guarantee or warrantee.