I've been having a look around for this but I can't figure out where to find it or what was being advertised. I remember this pretty clearly because when it was airing people were actively speaking about how sad it made them.
The advert aired in the early 2000's somewhere between 2003 and 2008 in the UK. It was live action and focused on a CGI moblie phone that was depressed that it's owner had upgraded to a newer model. The phone looked like a Nokia 5110 or 5160.
The ad opened up in what I think was a cafe, and the phone had been abandoned there. The phone becomes sentient and leaves the building and begins travelling down the street, at some point it passes it's owner speaking on a new phone. The ad was backed by sad music but I'm not sure if it was a specific song.
This summary isn't great and probably sounds a little silly, but it's been bothering me and I'd really appreciate if someone could ID it for me.