EBay a-hole issue with buyer?

A little over a week ago, I sold an iPhone to somebody. All went well until last night where he just sent an email out of the blue 4 days after receiving the phone. He claims that it is broken and wants a refund. He doesn't say how it is broken and refuses to provide evidence and he said he took it to a T-mobile store.

I told him that I inspected the phone 2x- one at my friend's house (I'm selling the phone for him) before I took it, before I shipped it, and the USPS guy even inspected it before double wrapping it in a firm shipping bag. It is impossible that I sold the buyer a defective phone. Because I told him this, I told him also to make a claim with USPS. Basically, he was like "nah" and afterwards used eBay's request a refund service to ask for a refund.

So realistically, he is claiming that he has a broken phone that he can't prove is broken and wants money back for it without doing anything about it. He then basically said, "I will handle this with eBay thank you" then sent me three messages that all were the same random letters and characters within a 10-minute time period.

Since he said that he went to a store of his cell phone service and claimed that they said it "wasn't able to fix," I'm going to call every store within 15 miles of his house to ask if a person with his name, address, or iPhone model came in to an employee between 3-7 November.

Any advice? There's no chance that I sent a bad phone.

EBay won't get involved beyond forcing you to take the phone back and refund the money. You are wasting your time calling stores to see if this guy actually tried to activate the phone because eBay won't care one bit nor are they required to.

What has most likely happened is the buyer is trying to switch their broken phone for the phone you sold them if you have proof the original serial # isn't the same as the phone that was returned then you'd have a case of wire fraud against the buyer.

EBay will make you take it back. That's their gig these days.
Take the phone back and give him a refund, or you will look really bad and eventually this sort of thing will get you kicked off eBay.
Once you have the phone back, you can recheck it. One way or another, this guy WILL get his money back- so go to eBay and offer to cooperate, because they'll return it anyway. These days, they're not backing up the sellers.

Prove It and you might have a case… Can't prove the phone was working and you don't! It's that simple!
P.S You need to talking to ebay or pay pal and check the Buyers Record to see if they make a habit of what you are claiming as well.

Drama

HOW is the phone broken? This is important to consider. Is it physically broken or does it simply not work with the buyer's service? Did you check and see if the phone would work with other services? For instance: a phone bought thru att won't work with sprint and vice versa. The technologies are different.