This post has been updated 12/11/14. The Zact phone number listed in the comments below is no longer active, and at this point, it seems like emails to email@example.com are no longer getting a response. The window to transfer a Zact phone may have closed, since the Virgin Mobile Custom people do not seem to know how to deactivate the devices and as discussed below, the devices remain actively tied to them even after a number has been ported.
A couple of users have reported that the "Virgin Mobile Angels" have been able to get their device released. The email address posted below is "SaveMe@Thevirginangels.com", and some persistence may be required.
It is possible that when Virgin Mobile Custom rolls out their unlocking policy (http://www.virginmobileusa.com/unlock) next year, the situation might change.
Ting has been great about trying to support phones that were sold by Zact. The current list is:
Samsung Galaxy Victory (PLSL300KIT) = Yes
Samsung Galaxy S3 (PLL710KIT) = Yes
Samsung Prevail 2 = Yes (confirmation from an actual user would be nice)
ZTE Awe = Yes
LG Optimus Elite = No, see below. Likely to be similar to the LG Viper.
LG Viper = Yes, but the ROM needs to be flashed to stock. Thanks Space Cowboy.
Instructions - http://androidforums.com/viper-4g-lte-all-things-root/633776-how-unbrick-lgls840-back-too-ls840zvc-ls840zvd-firmware.html
ZVD to download - http://d-h.st/nP6
Other details for making the switch are below.