You basically have to wait until your account is 18! That's when you're able to acquire open chat. You can also switch accounts and work on a new one, or you can basically email Kingsisle about it.
It's really simple, if you ever do get open chat though, don't disable it. If you go to your settings and disable it you can never get it back, but you can disable text chat though.
Chelsea Drake, lvl 86 Keira LegendBloom, lvl 64 Chelsea Thunger, lvl 25