From their "What's the Catch" Page 550 minutes, 150 texts, and 300 MB of data using the cell (non wifi) network is what they refer to as their "fair use threshold" and they say that you will get a few warnings to use less cell data and more wifi. If you continue to go over, your plan will be cancelled. Or in their more polite phrasing "they'll help you find a traditional cell provider that is better suited for your needs"