Sprint seems like it will be a good choice, they have cheaper plans without seeming like a disreputable company- but once you've signed up, set up automatic bill pay, and feel comfortable with your phone- that's when they'll start adding confusing charges. As many on this site have also experienced, their customer service in the billing department is obstinate to the point of being dismissive (while acting like they're being polite).
Finally, and what prompted me to take the time to write this review was that in canceling the service, they tried to not refund the "deposit equivalent" I had to pay one month in advance when starting service. This billing policy keeps each bill essentially paying for one month ahead, which is no problem until it comes time to stop service they have refused to refund that full month payment (while keeping me on hold for almost 30 minutes!)
Product or Service Mentioned: Sprint Account.
Monetary Loss: $156.