update your phones listing of cell towers in the area. its usually a simple code you enter and the phone downloads the latest data.
i went from getting 0-1 bars intermittantly to 0-4 bars intermittantly.
keep in mind that if you work in an office building, you might not get strong signals. all the steel used in construction tends to disrupt them. also, are the problem areas in spots where you experience bad signal during phone calls? you might live in/near a dead zone.