It's an oversimplification but basically T-Mobile.

The cheapest monthly plan you can get through T-Mobile is $29.99 which gets you 300 whenever minute, unlimited free weekend minutes, and free long distance and roaming. Sprint's Basic 200 plan is nearly as good, while it only gives you 200 anytime minutes, it also gives free Sprint roaming, unlimited free weekends and adds unlimited free minutes after 9pm.