Banning from Competitive only happens if you've done [i]a lot of quitting already[/i] and you have been suspended before as warnings. You were likely just suspended, which lasts only 30 mins. The system treats any left match, regardless of the circumstances or reasons, as quitting a match. It cannot tell the difference and Bungie has neither the support staff or time to have staff individually reverse every loss when someone claims being innocent. Your best option is to report the players of the team you last matched with for cheating and let Bungie investigate. If they find any evidence of network manipulation, they will suspend or ban those players.