Jessie doesn't call Ali on her cell phone. CH shows up at Ali's door, tells her someone needs to talk to her, then he goes to the phone in her room & calls Jessie. Of course, the call was arranged. The time differences would have to be worked out & it would have to be arranged that Justin's gf would be at Jessie's at a particular time when Ali was available to talk. I wouldn't be surprised if the scene where we saw Justin's gf talking to Ali was re-shot when they got back to the US. They maybe just used their voices for the actual call, then filmed the two girls at Jessie's pretending to call Ali at a later date.