I sold an item on ebay but don't want to sell it anymore?

So my friend gave me his iphone 6plus and i sold it on ebay because it was broken and had to be unlocked for me to use it but i found a place to fix it cheap and unlock so now i don't won't to sell it anymore

You'd better refund the buyer immediately with an apology.

If it is already sold too late. But read here http://smallbusiness.chron.com/remove-items-ebay-55189.html

You are a fantastic example of why 15 year old children are prohibited from using eBay. Hopefully this will get your account suspended. Good riddance.

Contact the person that won the auction and tell them you changed your mind. As long as no money have changed hands, no harm no foul. If they have already paid you, you have to refund their money.