Malfunctioning IPhone 15

My partners new iPhone 15 has started turning off when the camera is opened, battery drops from 80% to 10% in 1 second and now can barely turn on. We’ve read this is happening to a lot of IPhones. We are currently traveling in South America for another 4 weeks before heading to the UK. If he buys a new phone in South America and takes his faulty phone to an Apple Store in the UK when we get there to be tested for a system fault and it is proven to be a faulty phone, would we be able to claim the new phone purchased in South America and refunded the price of the new phone? (Note - the faulty phone was purchased in Australia where we are from).