Settings -> Wireless Settings -> Sim & Network Settings -> Click on a sim (SIM 1 or SIM 2, this one is dual sim) -> Scroll to the bottom of the list and click on SIM Toolkit.

Where do I find SIM Toolkit?

It is located a your Apps Menu with all of your other apps.

• The SIM Toolkit app is the control center of the KnowRoaming SIM Sticker.
• After applying the SIM Sticker to your SIM card and putting it back into your phone.
• The SIM Toolkit will be available in your Apps Menu.

What is a SIM Toolkit on Android?

SIM Application Toolkit (commonly referred to as STK) is a standard of the GSM system which enables the Subscriber Identity Module (SIM) to initiate actions which can be used for various value-added services. The SIM also gives commands to the handset such as displaying menus and/or asking for user input.