SIM Applications Toolkit (STK) is a GSM standard that enables SIM cards to start actions that can be used to deliver value-added services. This is the SIM Menu loaded by your for them to offer you more services. Some of these value-added services can include mobile money payments, substitute to USSD codes with a more interactive user interface, and more.
iOS update 12.1 and later changed the location of SIM Applications and placed it in a more logical location but still under settings. Go to Settings > Mobile Data > SIM Applications. Mobile Data in some regions is named Cellular Data and the steps remain the same.
Where is the SIM application on iPhone?
SIM applications on iPhone is located under Settings > Mobile Data > SIM Applications.
It used to be under Settings > Phone but has now been moved to Settings > Mobile Data.
This change started with iOS 12.1 and is still present in iOS 13 and 14. This is where you can get your SIM Toolkit menu option similar to that on Android phones.
It is significant to note that it is also where you can get your iPhone APN settings. It is under Mobile Data Networks and you can use them to access the internet as it is unique to your carrier/ mobile service provider. Network selection and SIM PIN are also located here.
Where is the SIM application on Android?
SIM Toolkit is a standalone Android app on Android called SIM Toolkit. To enable the missing SIM Toolkit on Android, navigate to Settings > Wireless Settings > Sim & Network Settings > Click on a sim (SIM 1 or SIM 2, for a dual sim) > Scroll down to the bottom of the list then click on SIM Toolkit.