kudos for asking...
it's really annoying when someone becomes squadleader by mistake...
what you can do is
1) go to menu (where the map and all the buttons are)
2)hit the icon with the TWO heads (2nd from the right) the social menu
3)then make sure you are on the top option="squad"
that should list the people in the squad with you
4)now all you have to do is aim your mouse the chevrons to the right of a name
5)right click with you mouse on the chevrons will open a menu
one of the menu items should read "promote to squad lead" (or even better "platoon lead")
6)select the promote option
and the problem is now his to deal with
steep learning curve
totally worth it!