Connection issues will never lead to a game ban. You were banned for something else. For security reasons and to protect the game, Bungie will never disclose the reason a player was banned. You can review Bungie's ban policy at http://bungie.net/ban. If you wish to appeal this ban, you can do so at the below link. You should note that there is never a guarantee Bungie will respond to any appeal. If you don't get a response, then it's likely Bungie has considered your ban correctly placed. Appeal - https://help.bungie.net/hc/en-us/articles/360049024492-Contact-Form-Appeal-Ban-or-Restriction