Time Travel

On the BBC site today, there's a wonderful story of how a film maker from Belfast has discovered a clip in a film from 1928 of the Hollywood premier of The Circus with what seems to be a woman walking down the street talking into a mobile phone: http://www.bbc.co.uk/news/uk-northern-ireland-11646933
Unsurprisingly, a short video made by the originator of the story has been a massive hit on Youtube.
Whilst it is a delightful story, there are a couple of moot points. Firstly, if someone has (at some point in the past or the future) travelled back in time to 1928 and was talking on a mobile phone, who were they talking to? Secondly, to use a mobile phone, there has to be some form of infrastructure in order to relay the signal to and from the phone, to and from a network that would then enable that person to speak to someone else. As, in 1928, no mobile network existed, it therefore follows that she could not possibly have been making a mobile phone call.
There is probably a perfectly innocent explanation for this. Either that or some wag somewhere has doctored the original footage and added the woman in order to create this story in the first place. Who knows?