The buyer is extremely cheap, but I have to go with you were being too greedy. Just cancel and refund the order next time. I am not huge seller, but it’s better to take a look from the outside prior to making an emotional decision. $11.00 won’t make a difference in the end, or getting your items back and relisting would make it back up.
You live n learn. Hope you can get the negative comments handled.
The buyer is not interested in hearing your internal process regarding updating listings in bulk and going from buy it now to auction. They saw your listings offer free shipping, they bought and you charged them shipping.
People are weird with shipping too and do not want to feel they are being swindled. I remember showing a person IRL a listing for a multiple-thousand-dollar charizard, and their reaction was “Why is shipping $100?”
If you make an error on the listing, it’s not the buyers fault. While buyer messaging is not always pleasant, telling them they are unprofessional isn’t going to win you repeat business.
live and learn
Received this today,
In my experience, buyers will bid lower than average on listings with S/H compared to free shipping listings to justify total cost of an item. For example, on a $5 dollar card with free shipping bids will usually near $5 whereas the same item with a $4 shipping bid will generally be maximum of $2 to justify overall cost of the item. This is why i was unwilling to offer completely free shipping. Maybe i am wrong whatever but lesson surely learned here.
so the motto for 2020 is:
ALWAYS DOUBLE CHECK YOUR LISTINGS BEFORE STARTING AN AUCTION! 
edit: enlarged image
To you being a Karen is expecting an accurate description on auctions?
Even that aside I think you missed my point. As a customer you’re allowed to be a bit upset if something goes wrong, you’re allowed to be a bit frustrated, etc. As someone who is the customer service position you aren’t really allowed that same behavior without possible repercussion. You can be 100% in the right but if you want to maintain proper customer service then you still need to maintain a reasonable tone and demeanor. I have worked across NUMEROUS customer service positions, you don’t always get customers at their best, but as a customer service representative they should get YOU at your best.
I would say I am the opposite of a Karen because I am looking at things strictly from a customer service perspective.
I’m not sure a customer support ticket trying to cancel the order is valid. If eBay stated free shipping on the listing and they bought something like a $10-20 BIN/auction then you going on the backend and asking for an additional $11 shipping is a significant portion of that purchase. They might not have been as nice as they could have but you also did not understand their situation as a buyer and you legitimately created a bad purchasing situation for them. You should have just eaten the $11 and moved on. None of the financial amounts I’ve seen in this thread warranted that much customer support and back and forth with a buyer.
So you’ve learned/discovered/already know what many have, and that is that one of the few eBay “positive” seller biases is that they like to keep the feedback of sellers clean when they can to keep buyer confidence high
I had a somewhat similar situation happen, i was selling a card consignment (gold star raikou). I had it listed in an auction and the description was something along the lines of “im selling this card consignment so in the end the owner of the card may get cold feet, ill send a consolation item if such is the case”.
Rough start, i know. It gets worse.
The auction ends around $80, i told the original owner and he said oh man i wanted way more, i feel like its worth $300… (it was a beat up copy, moderate whitening and a pretty noticeable crease). I told the auction winner that the card owner was not happy with the auction and wanted more money, which i didn’t expect -auction winner- to fork over. The auction winner was very upset, threatened to give me bad feedback, and told me its not my fault, i shouldve put a reserve or something or other, which was true enough. (Just from reading the way your buyer wrote his messages i feel they could be the same person) so anyway what ended up happening was i told the card owner i would cover an additional $80 if it would sway him in the direction of selling, i also mentioned some things about the card not having as high a value as he thought, it had damage, showed him recent solds, yada yada yada. Moral of the story is that as a seller, sometimes it takes money to make money, i kept my 100% feedback and due to that ive made back the $80 no problem, i also learned when selling consignment i need to establish some ground rules and expected returns with the owners.
Yikes…to literally all of that.
We all make mistakes. I remember when I auctioned off a watch that I paid probably $250 for and sold for $80. Did it suck yes? Did I complain? (probably in my head lol) I took the loss and learned from it. You win some and lose some. Sometimes auctions go way higher than expected and some not. I agree with pretty much everyone who wrote a response, at least it was just an $11 mistake and not much higher.