Also, there was no Holocaust.
ok, i'm going to be seriously for a moment... even if she did go back and did take a phone, the fuck is she talking too?
there were no mobile networks to connect too!
sorry to burst your theory but...
Cell phones are useless without infrastructure like cell towers / carriers / or sattelites. I kinda doubt virgin is sending people to history to build infrastructure so people can tweet their location at a chaplin premier?
Might it be a walkie talkie?