Android - How do I block this (carrier) advertisement dialog?

From what I can see from this site (In Spanish): this is a specific advertising service that only the Movistar network seems to push to phones.

The only solution I found is to Disable the "SIM Toolkit" application, Settings > Applications > SIM Toolkit but this may require root access to your device. Removing SIM toolkit according to Android Forum users can be removed without any issues. I would Disable it rather than take the nuclear deletion option personally.

From the link:

Hasn't been on my phone in a year... no problems without it - that I'm aware of.

and

I know for a fact that 4G works without it... has not been on my phone for the last year - and every ROM I could flash made no difference. I'm really temped to believe that SimToolKit is for Metro's various services/bloatware (where they monitor data usage - for whatever reason)

From Wikipedia:

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.

These so called 'value added services' are what you want to remove.

Alternatively you could contact Movistar and see if they can stop it, tell them it is crashing your device or causing you issues and ask what can be done. Depending on your contract you could move to another network also.

I was getting tired of those messages too, worse of all, the text was always garbled.

If you already have Titanium Backup Pro like I do, I simply "Froze" the SIM Tool Kit app. It disables the application and prevents the icon from appearing in your app drawer.

If you were ever to need it you can unfreeze or "Thaw" the app.

So far I've never seen the use of the STK. If I didn't have the backup app I would delete it without thinking twice.

Go to SIM Toolkit and search for Flash services and deactivate it. Worked for me.