Placing a wrong bid can be a big suck when it comes to buying products through auction. Say thanks to eBay for understanding this problem as eBay lets the users to change or cancel bid on eBay. Though there are some preset terms and condition according to which anyone can retract bid on eBay. All those terms and conditions are explained in this helping post: https://quickutilities.net/blog/how-to-block-buyer-on-ebay