A:Answer I've seen some problems with Movistar signal and blu cellphones that are only 2g & 3g
For example, you are in a room and suddenly the cellphone has "Emergency only" instead of "Movistar". So you have to take your phone to a windows or go outside. Turn the blu cellphone off and turn it on to see if it gets the signal again. Not always happen. Sometimes you have to do it several times.
This i've seen it in various blu phones, same and different models but only the ones that are 2g & 3g
Regarding your other question you can usea any slot for Movistar or another cellphone company.
good luck!