How to prevent phone operator from opening spam popups?

My phone operator, Movistar Argentina, is sending a lot of spam. I managed to block most of the SMS, however it has now also started opening ad popups on my phone (see below).

I've looked at How do I block this (carrier) advertisement dialog? but I cannot find the "SIM Toolkit" app anywhere on my phone to disable it. Is there any other way to block this?

Answer

If that can help someone, the app I needed to disable was /system/app/Stk.apk and it was called "Services SFR v4.1.2-LL__zg".