With a new account, you don't. Most buyers would run away from new accounts selling iPhones. Maybe eBay has institutionalized that running away.
Yeah that's fair, I'm facing the same thing with credit, since I just moved to the UK.
Buying and/or selling other items to build up your feedback first (My current account is 12 years old, and I have sold several iPhones there, 2 recently, with little issues, though you don't have to watch out for scam attempts)