A typical smartphone costs around $200, but it's usually shackled to a two-year contract that often costs $70 or more monthly and includes limits on data consumption, voice minutes and texts. Even prepaid smartphones, without a contract, can cost $30 to $50 a month and carry limits.

But I've been testing an Android smartphone from an upstart carrier that charges just $19 a month for unlimited data, voice and texts—with no contract. That's right: $19 a month, unlimited.

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