How do I "upgrade" the OS on my blackberry 9900? The battery life on this thing is embarassing, to the point where a 10 hour charge then last about 3 hours. I have removed apps like FB and Twitter from it but its not really had much impact. Some places suggest trying the latest OS - but I can see how to upgrade. Others say even using the phones lock key has an impact which sounds strange. Any other tips aside from upgrading the OS?