Useless service

Hi. I went to I store in east rand Johannesburg. My phone is over heating. iPhone 15. I explained to the lady and she tells me it’s normal for iPhone. I got angry. I bought the iPhone in January. Still new. I went to manager. They checked the phone on the computer. They say battery problem. The want to send it in and I must wait 7 days. I want a new iPhone. I’ve been using iPhone since iPhone 3G. I will not buy iPhone again or apple products again if they don’t make a plan