Esto es lo que me dicen el foro de XDA. Probaré a llamar otra vez a movistar a ver si tienen constancia de este fallo general.
I had a quick search on Google and this is not an isolated incident. Users with phones from Sony and Samsung among others have been reporting the same issues with the movistar network after upgrading to ics. Some have found a factory reset fixes their problem, I don't know if you have tried this yet.
It could also be an issue with updating via ota, so here's a link to the ruu if you would like to try that instead (thanks maverickdbz)
http://d-h.st/7UC