In episode 13 of Season 1, Escobar Gallardo, in the part when Christian is calling Sean on his cell phone, it shows him searching for S, and Sean's Cell shows up on the list. He hits dial, and it goes to the dialing screen. If you look on the left side of the cell phone display, it has 0 bars of service. Nokia phones [like the one he is using] won't work if they don't have service. However, he puts it up to his ear, and you can hear the ringing. He then leaves a voice mail. Then he hangs up.

This is at minute 36 second 38