I'm not sure how the companies work in the states, but here in Canada, the companies will try to keep you from switching providers. Their phone line has a retention department specifically for this. So if you call Verizon, they may cut you a deal to keep you from switching.
I don't think changing carriers is any different at the carrier store or Apple store, but I imagine the carrier store might be able to give you some deals, like a free case or a discount off accessories? You could probably walk in and ask what benefits there are to switching providers here.