Welcome to Android Central! I assume this is the LTE version, since it sounds like you got it from a wireless provider, right? Is it the 2012 or 2013 version? The 2013 is the one with the rear-facing camera.
So you got it last December--but when did it start failing? Was it right away, or just recently? I can't quite tell from your description. Did you talk to the wireless provider about the defective device, or are they the ones who directed you to deal directly with Asus?
Which app did it freeze on? In the future, if the tablet freezes, you can press and hold the Power button for about 10-15 seconds, which will force a power down. Then you can turn the tablet back on again.
In terms of trying to power back on again, check out this support page:
https://support.google.com/nexus/troubleshooter/3337561?hl=en
Also see if you can boot into Recovery Mode. If so, wipe the cache partition, which won't erase any personal data, but might help to resolve an issue like this:
http://forums.androidcentral.com/go...e-nexus-7-2012-2013-cache-partition-wipe.html
You can also consider booting into Safe Mode, which temporarily disables all 3rd party apps. If the problems stop, then something you installed is making the system unstable--you'll have to uninstall apps one by one until the problem goes away.
https://support.google.com/nexus/answer/2852139?hl=en