Did you purchase your device from ShopBlackBerry or Amazon and not get the BlackBerry 10.3.1 update yet? If so, here's a little something to try that might force the update to arrive on your device though it does seem as though the results are still mixed.
ShopBB purchased and not got update? Power off, remove sim, restart wifi only. Check for updates. Power off, re-insert sim, continue.— Michael Clewley (@MichaelClewley) February 24, 2015
If you're still waiting for the update, go ahead and give that a go and let us know how it works out in the comments for you personally. If you don't follow this procedure, your device will still get the update, it'll just take a bit longer.