Not unless the winning bidder doesn't want it any more. Has the winning bidder asked to cancel? If not, you have to honour the sale, or you risk negative feedback and a defect for your efforts. You only have low feedback, a negative could impact you badly.
It wasn't a phone you sold was it? Scammers will often offer a far higher price for items and want you to send it somewhere overseas (usually somewhere in Africa as it's a gift for a relative).
