I bought an iphone 4s from ebay, and within a couple of weeks it developed a fault. Seller offered to repair so I returned it, at my own cost of nearly £8 and they fixed it. They replied really quickly but I didn't contact them through ebay, but via an email address they gave me on the warranty. It's now got a different fault and the phone is completely dead so I contacted them again, this time through ebay, asking for a refund. I've had no response, nothing and it's been 5 days.
I've never done this before, so how long do I wait before I ask ebay to sort it out? Any other advice on getting my money back?