from http://www.engadget.com/2012/10/01/freedompop-launches-in-beta/
If you're trying to avoid all charges, you'll have to be very,VERY careful. Charges are lurking everywhere. Plan on using this only for backup internet? If you don't use 5MB in a particular month they will inactivate you and charge you $0.99 for every month you're inactive until you either pay to reactivate or cancel altogether. If you do cancel, it's $19.99 to reinstate your account. Usage alerts cost $1.99 per month and a modem warranty costs $2.99 per month. If you come within 100MB of your limit and you have $2.00 or less credit on your account, you'll get charged $10 on the credit card that they keep on file as a result of their automatic top-up "feature". You're given the illusion of being able to opt out of it, but if you do, your account automatically gets put into a suspended state which goes away when you re-enable it. So that lowers your actual free usage to 400MB.
Just so everyone is clear, the device is only refundable within 30 days per their FAQ! After 30 days, you'll have to keep it.
