Essay writing services do not plagiarize. They provide guarantees of plagiarism-free content and do not tolerate copying content from other resources. Many supplement their completed orders with a no plagiarism report - a free-of-charge document testifying the 100% originality of written content.
Permitting plagiarism would in most cases lead to the inevitable demise of essay service. It is a matter of trust and reputation. An unscrupulous service will quickly lose its clients and cease to exist. So, you can rest assured that the current popular essay writing services won't sell you plagiarized content.