It depends really. Mine has only even frozen once ever in 3 months and that was my fault for installing an app I knew was bad.
Anyway, have you tried a proper hard reset? If not then you should. Don;t know where you are or what network you arte with but another thing to try is to set the max connection speed to 3G for the moment.
No, leave it on 2G. I thought you might have been on 4G.
You can reset using Settings>About>Reset your phone, of have you already done this?
If you have and the problem persists then perhaps you should contact Nokia Care again.