Some interesting clips about time travelers possibly caught in the act, talking on cell phones.

But you have to question:

1. Who were they talking to.
2. How did they get signal, or were the devices working like intergalactic walkie talkies.
3. Or were they talking on small hand held radios?

OR... given that the Nazis had developed a lot of interesting technology by the time these film were made it might be that cell phones already existed by then. The common people do not get to see technological innovations sometimes for a full generation after they were made. The cell phone came out to the public in the 80's I think? Not so recent.