jake's cell phone?

Is that all you could comment about? I don't know where u reside but where I work people have two phones. One for work and the other for personal reasons. Also people change phones ALL THE TIME. Phones are not as expensive as they used to be. Personally for me a phone is a device to recieve and give calls so it lasts a couple of years with me, but others who are into latest technologies and phone trends change on an almost monthly basis. Jake seems to be the second type so its probably on purpose.

The initial pilot had a scene where Jake's cell phone was stolen. It ended up on the cutting room floor...but this would explain your observation.

It is a TV show, and things on TV do change...

I too noticed this (he has a Motorola V710 in the pilot, as does another character, but something else in the second episode). But note that things often change from the pilot because they are often shot months before the show goes into production. Sometimes even actors are changed.