remove a text account.

How do I remove a TEST account set up during an Apple Support Service call? I tried the suggestions (I went to system settings, users and groups, and clicked on TEST icon), but a checkmark was in the icon. The FileVault is locked. I looked at one suggestion about what to do next, and it is ridiculously complex. Also, the Apple support person said the test account was removed, why isn't it? I'm worried that there has been unauthorized access to my computer due to the checkmark (meaning "used") on the test icon.