This number simply doesn't work. When you dial this number, all you get is a message from your cell phone provider saying that the number has been disconnected and your call cannot be completed as dialed. Given that FreedomPop is billed as offering free mobile services to its customers, that's kind of surprising that you'd get a disconnection notice.
It appears that FreedomPop does still exist, but it now operates with a different phone number: (888) 702-8302. Calling this number simply won't work, and any searches for this phone number don't return any links for FreedomPop's website. It seems that the company has taken down any mention of this number on its official channels, and this number was fully disconnected and removed from FreedomPop's network.
FreedomPop's own website suggests that it still offers customers the same items it did when it used this number. It appears that it's now marketed as a call service for seniors, however, which means a full break from the old number might not have been the best solution. Many seniors do write down all of their important phone numbers, and simply disconnecting without leaving a message on how to get to the current number might make it difficult for seniors to find out who they really need to call.
Based on this experience, there's absolutely no reason for anyone to use this number.