@socialmediaseo I agree it's not a good way of doing things, it would likely help to inform users of what they're doing and how to resolve. A simple message in the comments in a post, then if ignored a downvote could be fair.

For example: "Please stop using SBI under new guidelines #newsteem we are stopping the use of paid vote services like SBI, please either get a refund or sell your shares to a 3rd party, if you do not do this by the time you post next we will downvote your post bla bla bla"