In contrast, opting for a similar plan from Sprint, which is one of the only big carriers still offering an unlimited data option, will cost you $99.99 a month for unlimited voice, data, and messaging.

How much can I save? $40 to $45 per month.

Next: Six More Cost-Cutting Tips for Your Cell Phone Bill

7. Go contract free: It may seem counterintuitive, but one way to lower your monthly cell phone bill is to go contract-free. This isn't the same as buying a prepaid cell phone (we'll get to that next); here, you still pay your carrier month-to-month for cellular service, but you pay less. The trade-off is that you pay more for the phone itself up-front. But depending on the phone you choose, you could save big in the long run with this strategy.

How much can I save? You'll pay T-Mobile $350 for its MyTouch Android phone, but you won't sign a contract. A from T-Mobile with unlimited talk, text, and data costs $59.99 per month, so the cost of buying and using this phone (spread over two years) is about $1790.