Refund for item that was faulty

Description

Hi there. I purchased a car radio unit from a secure website. It was posted from China. The product is faulty and I would like a refund. I have contacted the seller and they have said they will issue a refund however this is where the issue is. They have said I need to send the item via EMS which I have not heard of. And they said I need to write on the package ‘$69.5USD’. The item was $608USD so obviously I am not happy to do this. They said this was to do with customs. I am now stuck as if I send it via Parcelforce it sounds as though they may not receive it and then I will be without the item or the money. Please can someone advise what would be my best option now? I have received an email from PayPal stating I need to send the item off within the next 10 days so would like to know what I need to do. Regards.