It is ironic that I am the one who stepping in here to give some insight.
Monte Vista is a store world, not an expansion pack, so that could be part of the confusion. With an expansion pack, you will get certain things along with the new town. With Supernatural, you get the supernatural beings, weres, vamps, witches and of course the zombies; who show up during the full moon. New traits are given, along with careers, LTW, rewards and skills.
With a store world, like Monte Vista, Aurora Skies and Dragon Valley, you can get new items, such as the Marketplace with MV, the Education Center with AS and the Bow Training arena when you buy the gold versions. I'm not sure, but I think you can buy them separate, at least some of the items and I am pretty sure you have to have the store world to be able to buy them at all.
The cell phone was something that EA came up with that is supposed to make it easier for players to move their families from not only one house in a town to another house in the same town, but to also move from one town to another.
The base game is Sunset Valley, so if you have a store world, such as Monte Vista and want to move there, you can use the cell phone to do so, instead of saving your family (with or without their house) to the bin and then starting up a game in that town and then added them to the town. Now, with just a few clicks, you can chose to move to that town.
I've not tried it to see if it works, others can give feedback on that, or you can look and see if there is any info in the Guide Carl has about it.
If the only game, or town, you have is SV, then the option will probably come up, but you won't have any selections due to not having any of the other towns.
I hope this has helped you some, and ask away if you have any more questions. This is a great place to come to for information. The members of the forum are great in helping out in whatever problems you have.
The irony that I mentioned is that although I know that MV, DV, AS and RV are store worlds, not expansion packs, I still catch myself calling them that. Which is why I caught that you called MV an expansion pack, when it is a store world.
If I have any information wrong, please someone correct me, as I would hate to give out inaccurate info.