Welcome to Fiverr.
You can help yourself! How? Ok, lets see how can you handle such odd moment!
You can just gently say your buyers that “It breaks my heart. You don’t seem certain things you want and asked the beyond what we agreed. So, I think it would be best for you to find another seller to complete your order.”
After saying this, the buyers may leave you or may go through the program. And if the buyers continue to threat you or make you compell do the extra work, you should contact with the Customer Support Center. But in those cases, you need to provide sufficient proof like providing screenshot between you and yours buyer conversation.
If you can supply the Customer Support Team required proof, then you can hope the judge will bring you smile. Your problems will be solved by CSC.