You are on managed payments, but obviously  dont know how it works,

Your buyers payment would have gone direct to ebay.  ebay would have advised you that your item had been paid for and that you were then required to ship the item (you do  not get to wait until the money is in your bank account before shipping), and as a new seller ebay would have placed your funds on hold for 30 days.

As you obviously refused/failed to meet your responsibility in relation to the sale, the buyer would have been fully refunded by ebay, and you would still be liable for all ebays sales fees and any dispute resolution fees.

Learn how the system works or dont sell