Vulnerable relative ripped off

[TheChosenTwo]

By being sold an iPhone 8 that doesn’t work with a handwritten receipt that says not refundable. Where do I stand? How can I help?

Oh sorry, I did mean to specify it was second hand, I meant independent as in a one off, not like a Vodafone or 02 or anything like that. In fairness and probably being a right snobby cow here it looks like one of those shitty kiosk type places, (but an actual shop) you know, it’s a phone shop now but in a few months time it’ll be a Christmas themed shop, possibly run by a dad and son. I don’t know, it’s the kind of shop I swerve by a mile and wouldn’t ever encounter going in because of the fear of being scammed! I’m not knowledgable about phones at all, I have had the same phone number for about 20 years and have a contract with the same company I took one out with all those years ago, every now and then they phone me telling me I can upgrade and I do. That’s about it!
It’s a handwritten receipt on headed paper.