How can I block a customer

[cherrypicked4u]

Customer made a purchase 9 months ago and keeps asking me questions and I don’t need this!!

[evry1nositswindy]

Block buyers from your listings:

https://www.ebay.com/bmgt/BuyerBlock?

You can block communication too, but since you've been in a transaction before, I don't think this works.  Just ignore the messages and hopefully they will go away.