T-Mobile has been my carrier for two years now and I love them.

Contracts are a year long and depending on your credit you could qualify for a free phone. If it's not the phone you want, the cool flip phones are offered at a discounted price.

After my first year they gave me an extra 50 loyalty minutes so now I have 650 minutes in my plan at no extra charge. For a phone upgrade you don't have to resign the contract. As far as plans I think they probably have the cheapest around.