From Amazon
When you purchase your device with service from AmazonWireless.com, we automatically pass along an instant discount from the carrier to you.* This discount has been provided to you based on your agreement to (a) activate a new, or extend an existing, line of service for this device with the carrier, and (b) maintain this service in good standing for a minimum of 181 consecutive days.* If you do not activate or extend a line of service in connection with this device, or if your service is canceled/disconnected before 181 consecutive days, AmazonWireless.com will charge you $250 per device, plus applicable taxes.