So basically everyone here is just flat out ignoring the fact that we tried it and it still worked. OK.
Contact FreedomPop's Twitter Support, and they should be able to get one of the devices deactivated so you can reactivate the device on a new FreedomPop Account. They normally respond within a day.
It will require a minimum 3G phone by the end of the year, though.
From who did you purchase?