You can not report them. You need video evidence thats max 5 mins long. Screenshots do not work for teaming.I have found two people teaming on solo sky wars how do i report? i have pictures
^^To report a player you go here:
https://reports.cubecraft.net/
And if you need to learn more about how to use the report system:
https://www.cubecraft.net/threads/how-to-use-the-new-report-system.175577/