Service - iPhone 15 pro battery life

I have the new iPhone 15 pro and my battery is draining quicker than it should. I asked them to assist me, when they referred me to another Vodacom in Emalahleni. When we got there they told me that they are not able to assist me. After a bit of convincing they helped me but only used my battery info that apple provide. I had done nothing on my phone that day and the battery dropped with 30%. They do not understand that my battery is dropping without me doing anything on my phone. My phone is still in the 7 day period but they do not want to exchange my phone and provide me with a new phone.