Back Market review: iphone se 2nd gen

I bought an Iphone from Back Market that DPD didn’t attempt to deliver to my house they took it straight to the post office which I couldn’t pick up for a few days. When I opened the parcel the box was damaged and the phone screen was cracked. I knew back market couldn’t replace it for 7-10 days so I went and bought a replacement phone that day and applied for a refund. They say all over their website that you have 30 days to return the product however when you actually go to return it (showing pictures and an explanation of why it’s faulty) they reply with an automated response saying you only have 3 days to return faulty goods. They have no contact number or email you have ti wait a number of days for automated responses on a chat line through their website where I got nowhere. It was just copy and paste messages saying how they can’t do anything because you only have 3 days to return faulty goods. I explained how this isn’t my legal right as a customer I have up to 30 days to return a a faulty item but they’ve just stopped responding, it’s been 2 weeks of me messaging them and no response, no contact details, no customer service, no refund.