Read through this page: https://help.bungie.net/hc/en-us/articles/360049497451-Report-Suspected-Cheating-and-Poor-Behavior It mentions multiple ways you can report them outside the game. Finally near the bottom there is a cheater form section that links to a contact form, it says it should only be used for reporting cheating but you can however use it to report poor behaviour by selecting ''Impersonation, griefing, and/or toxic behavior' in the 'What specific behavior did you see that you believe to be cheating?' field.