As Irina_Spitznagel said you can activated or deactivated the mobile data of the currently chosen data-sim quickly via the notification bar.
but what did work better on my ZTE-Blade-C jellybean dualsimphone was switching the data-sim via notification bar (which should be added via shortcut in notification bar or shortcut) and remembering settings like which simcard should be data-sim after reenabeling it or changing phsical simcards 3rd or 4th sim in pocket