Give it a few weeks and see if you're still getting it for free
.
I've seen people with other devices say the same thing being said here the first few days with their new device, although their prior device also had Sprint Navigation, but didn't work because they didn't pay for it.
And some days later they came back saying the free ride ended, no pun intended.
Given the new install of Telenav after the ROM flash, you're being granted a free trial.