One more note: when trying to receive a call with the Yoigo SIM, the phone doesn't ring at all, nor display any message, but I get the missed call in the call log!!

And when I'm on GSM the caller gets the voice prompt: "Movistar info: this option is not available" , Yoigo uses Movistar network in GSM, as I already commented. This is quite weird, as callers might think I am a Movistar customer, but I'm not.