I sold an item on ebay?

[Carly]

I sold an item on ebay, and it went for far to cheap, I wrote on the description that I would need immediate payment, the item ended at 6am and the I sent the buyer an email at 11am saying I will not need payment as the item hasn't been paid for and I ended it because it was now 11, anyway the buyer ignored my email and paid at 3pm I told the buyer I would immediately pay back the refund, which I would, but now they are refusing the refund and demanding the item. Who is in the wrong here, do I have to ship the items, or can I just give them a refund.
I do not want to send the items, as they went for far to cheap.
I tried to end the item, but because it was ending in under 12 hours, I could not end.