T-Mobile hands down.

I pay $44 for unlimited everything. Note that the low monthly payment is due to having 5 others on a family plan and I am not paying monthly for my device on top of the service.

T-Mobile has a T-Mobile Tuesday app, which they give free stuff and discounts to members. Some weeks they're good, some they are pretty awful, but hey - can't complain about free stuff.

The service is excellent. I recommend.