Any particular topic? - you can start here, unless it's personal account related, and we may be able to help, or can direct you to eBay contacts.
If you want to reach eBay CS, follow the instructions below all the way to the end to Chat live with an agent, or have an agent call you back.
Pick a topic "close enough" to your issue so that you reach the right team.
Tip - when the Chatbox opens, type in "Agent", then press "Send" to bypass the bots.
https://community.ebay.com/t5/Selling/How-do-I-contact-Customer-Support/m-p/32016431#M1783851
Note: The Call Back option doesn't always work if your carrier blocks spam/telemarketing calls. You may need to disable it first.
With the Chat option eBay will automatically email you a transcript.
