any advice for reducing our monthly cell phone costs?

My husband needs an iphone for work, I just use an old flip phone. We are paying ridiculous amounts with AT&T right now. My husband's phone is not under contract with them, but mine is- so I can switch him to something else but I"m stuck with AT&T.

Anyone used StraightTalk? It looks pretty good.... He is still using an old iphone3 and is going to need to upgrade soon. Is there a way to get less expensive iphones?

I'm totally clueless about how they work (SIM cards? refurbished? help!) which is why we've just stuck with ATT for so long. But honestly I'm starting to feel a little used by ATT- no perks for long time customers!