Has anyone had success with revoking ACH withdrawal

CFPB had once taken action against this company for using illegal debt collection practices. So, you can complain if they're harassing you.
About ACH withdrawals, write to the company and the bank to revoke the authorization.
Moreover, if it's an illegal loan, you're just supposed to pat the principal amount.

Not an issue. There are many members in our forums who have revoked ACH authorization. So you can also do it. Not an issue.

Here are a few pages where you can get more information:

https://www.debtconsolidationcare.com/forum/paydayloan/successinrevoking-achaccess.html
https://www.debtconsolidationcare.com/forum/paydayloan/getacallfrommy-comanageratwork.html
https://answers.debtcc.com/Payday-loan-consolidation-and-help/Please-help-wiith-USA-Cash-Express.html
https://www.debtconsolidationcare.com/forum/paydayloan/supposedtocomeout-tomorrowmorning.html

Yes, you can. You just need to approach your bank properly.

Send your bank an Email mentioning the ACH details and ask them to revoke the process with immediate effect. That'll do. Once done, put the due balance into your account and close it if you want.