First of all, remember that Wattpad will only contact you about problems directly, not by messages on your board. These scammers are useless, but it’s easy to make a mistake.
Secondly, I urge everyone to check Google Play books, where a large number of books have been stolen and put on there. It’s relatively simple to fill out the take-down request. @Romizabooks has a few links on their wall for you to check.
I hope no-one else has had their work stolen, but have a look anyway.