I have read about this issue a couple of times in the forums. And I am afraid there is no clear solution. The best bet would be to contact Everlink and see if they can upgrade the phone.
http://support.everlinkwireless.com/
They have a link for the upgrade. And I also hope they are still doing it

I must warn you that they dont have the best support.
And have you tried Hard Reset?
- Take Battery out.
- Put it back
- Plug the power cord to the phone
- Hold down * and 3 keys simultaneously
- While doing that Press Down on the Power Button
- That will bring up the erasing IPSM screen
- Wait for it to complete