A SD card cannot format itself.
It is formatted by a command from the device/computer it is being used in.
While the 16Gb card is still in your computer, can you access the card... read files, and copy files from the 16Gb card to an empty folder on your computer?
1st, make sure the cards lock tab is in the UNLOCK position. That's up, or towards the end of the card with the contacts. You should be getting a write protect message if it's locked, I'm just making sure.
2nd, are you sure you are transferring files to the SD card, and not another hard drive or removable media on your computer? I've got drives C thru K on my system, and it's hard to keep up with sometimes. Just checking.
3rd, it's possible, but unlikely, that the cards FAT table is corrupt.
If you are on a Windows system, do a disk check on the card.
Double click My Computer / right click the cards drive letter / select Properties from the drop down menu (last item on menu) / click the Tools tab / click "Check Now" under Error Checking / click Start
It will take about 30 seconds. If it finds no errors, you might do it again but check the "Scan for and recover bad sectors" option. This takes MUCH longer, but it will make sure each sector on the card is readable.
If the card checks out OK, but still won't hold data, just go to you're local Verizon store and see if they will swap out the card for you.