By going off brand you can often find cheap cell phone plans if you shop around. If you are paying for voice and data in your plan you can expect to pay a little extra. The cheapest cell phone plan that I've seen is the prepaid Go Phone. You can get started with a no-contract cell phone service for about $15.
Alternatives to paying your phone bill
You can save money by switching to a VoIP service such as google voice. Google voice is a free phone service for calls within the country.