How do I stop joining a group (or leave a group)?
By default the game settings check the player's chosen options when auto grouping any gamers that are close together near encampments and engagements.
You can change this setting by going into the Menu by pressing the escape Escape (Esc) key, or using (clicking on) the Menu Icon down in the lower right corner of your game screen.
Select the GAME button at the top of the menu.
There is a check box for 'Enable Auto-Grouping' [ ticked by default ] that will disable the auto function if unchecked.
The 'Auto Leave Auto-Group' option, if enabled, automatically removes you from any Auto Group when you leave an engagement area.
You can type /leave to leave a group you are currently in.